an essay on human understanding summary

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An Essay Concerning Human Understanding by John Locke is one of the great books of the Western world. It has done much to shape the course of intellectual development, especially in Europe and America, ever since it was first published in 1690. Few books have ever been written that have so adequately represented the spirit of an age or left so great an imprint on so many different fields of inquiry. Although the main subject matter of the Essay is primarily a philosophical one, it has had a direct bearing on such areas of thought as education, government, ethics, theology, and religion. Indeed, there are few disciplines in the field of higher education that have not been influenced to some extent by the ideas set forth in this monumental work.

The importance of the book is well indicated by the number of editions that have been published. Between the time of its first publication and the author's death, four editions had been printed, and since that time more than forty editions have been published. Scholars in each succeeding generation have become acquainted with its contents, and in many instances they have made replies in book form to the arguments presented in it.

Because the Essay deals with a subject that is of vital concern to every field of knowledge and because the author was held in high esteem by authors and men of affairs who were contemporary with him, the book became at once the subject of criticism and the occasion for many vigorous controversies. This was in a sense what Locke had hoped his writing would accomplish. He was not a dogmatist, and he made no pretense of possessing a store of wisdom to be passed on to others. Rather, his purpose was to stimulate others to think for themselves, and what he had to say was intended as a means toward that end. In fact, it was one of Locke's major ambitions in all of his writings to dispel the sources of intolerance and encourage people to promote the cause of freedom in their thinking as well as in their actions. Many of the freedoms of which we boast in the Western world today are due in no small measure to the work of this man.

Among the critics who have expressed their views about Locke's work in writing, one finds both praise and condemnation. This is due in part to the fact that not all of them have interpreted what he had to say in the same way. Each critic has viewed the work from the perspective of his own experience and understanding. Each one has come to it with his own presuppositions, and these have been bound to influence the judgments made concerning it. To some extent, this is an unavoidable procedure, and one must deal with it in the best way that he can.

The Essay Concerning Human Understanding was the first work of its kind to appear in modern times. It was an attempt on the part of the author to make a serious and systematic inquiry in the problems of epistemology. It marked an important beginning, for once the inquiry had been brought to the attention of a reputable group of scholars, it became the central issue in the philosophical discussions that took place during the next one and one-half centuries. In fact, the movement that began with Locke was continued by Berkeley, Leibnitz, and other writers of distinction. It reached in one sense a culmination in the philosophies of Hume and Kant.

After Kant, interest in epistemology was replaced to a considerable extent by other topics, which dominated the field until the early part of the twentieth century. After the close of the First World War, a new interest was developed in questions concerning the nature and limitations of human knowledge, and once more the problems that were discussed in Locke's book were given consideration by scholars who were working in many different areas of human experience. While it is true that many of Locke's conclusions are rejected by philosophers of the present time, the spirit of his inquiry may still be regarded as a dominant characteristic of the thinking of the present day.

Any adequate appreciation of Locke's work must take into account the circumstances under which the book was written, as well as the major objective that the author had in mind. Many of the criticisms that have been written about it appear to have overlooked one or both of these points. For example, it has been fairly common among Locke's critics to call attention to the fact that incongruities can be found among the different sections of his work. That instances of this kind can be found when one reads the entire book must be admitted by anyone who has read it with care. But at least a partial explanation for this fact can be seen in the way in which it was composed.

The Essay was not the product of a continuous period of writing. It was produced a little at a time over a period of more than twenty years. Obviously, some changes and modifications were bound to take place as Locke gave added consideration to the questions that were involved. Besides, he made it abundantly clear throughout the Essay that he had no intention of speaking the last or final word on the subject. All that he intended to do was to set down the best thoughts that had come to him at the time of his writing. This he did with the hope that it would stimulate others to carry on a similar inquiry in their own minds.

In an epistle to the reader which forms a kind of preface to the book, Locke tells us how it was that he became interested in this type of inquiry. It all began in a series of discussions that took place in the company of a small group of friends who had been meeting at regular intervals to exchange with one another their views on important questions of the day. Evidently the topics for discussion included such subjects as science, morals, religion, and their relation to one another and to other disciplines. The fact that the members of the group seldom reached any agreement among themselves and often failed to reach any definite conclusions at all caused him to wonder just what benefits, if any, these discussions might have. The more he thought about it, the clearer it became to him that any progress which might be achieved along these lines could come about only by giving careful consideration to the possibilities and the limitations of the human mind.

If one could find out what it is possible for human minds to know and what are those areas that cannot be known, then one need not waste time on those questions that cannot be answered. Again, it would be most helpful to find out those areas, if any, of which we can have certain or absolute knowledge, as well as those areas in which we can never obtain more than probable knowledge. It was the pursuit of these inquiries that led to the writing of the Essay. The task that he set out to accomplish was far more difficult than he was aware at first, and reflection on the issues involved over long periods of time led to many changes and modifications.

The Essay as a whole is a lengthy piece of work, and it is not unusual for those who read it at the present time to become lost in the detailed accounts that are included in it. Many of the words that are used are ambiguous in their meaning, and the ways in which they are used are not always consistent with one another. Further difficulties arise from the fact that words do not necessarily have the same meaning today that they did at the time when Locke wrote. His purpose was the very practical one of helping people to think more clearly about the problems of everyday living, and as a means toward this end he used language in the sense in which it was generally understood at that time.

Technicalities in connection with the use of language with which we are familiar at the present time were not recognized by the average reader in Locke's day, and this accounts for some of the misunderstandings that have occurred in connection with the interpretation of his writings on the part of more recent critics. But these difficulties are relatively minor and should in no way obscure the major objective that Locke had hoped to accomplish.

The primary purpose that seems to have inspired all of Locke's major writings was his intense devotion to the cause of human liberty. He was unalterably opposed to tyranny in any of the forms in which it had been manifested. This included not only political tyranny but moral and religious tyranny as well. The age in which he lived had witnessed the results of tyranny on the part of both political and religious institutions. In the field of government, tyranny had been supported by the theory of the divine right of kings. In a somewhat similar manner, the authority and prestige of the church had been used to coerce individuals into acceptance of what they were told to believe and to do. To all of these devices for controlling the minds and activities of men, Locke was opposed. His views found eloquent expression in his Treatises on Government and his Letters on Toleration. The same objective, although expressed in a more indirect fashion, can be attributed to the Essay Concerning Human Understanding.

Because the freedom of the individual to think and to act for himself necessarily entails a sense of responsibility to exercise these freedoms in the best possible manner, anything that would help to prepare people for this task would be in order. As Locke saw it, nothing would help them more in this respect than a better understanding of the processes that enable human minds to arrive at truth. Furthermore, an appreciation of the limitations of the human mind would encourage an attitude of tolerance toward individuals holding different and conflicting opinions. Tolerance in human society would tend to be a safeguard against persecution and the evils that are necessarily associated with it.

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John Locke (b. 1632, d. 1704) was a British philosopher, Oxford academic and medical researcher. Locke’s monumental An Essay Concerning Human Understanding (1689) is one of the first great defenses of modern empiricism and concerns itself with determining the limits of human understanding in respect to a wide spectrum of topics. It thus tells us in some detail what one can legitimately claim to know and what one cannot. Locke’s association with Anthony Ashley Cooper (later the First Earl of Shaftesbury) led him to become successively a government official charged with collecting information about trade and colonies, economic writer, opposition political activist, and finally a revolutionary whose cause ultimately triumphed in the Glorious Revolution of 1688. Among Locke’s political works he is most famous for The Second Treatise of Government in which he argues that sovereignty resides in the people and explains the nature of legitimate government in terms of natural rights and the social contract. He is also famous for calling for the separation of Church and State in his Letter Concerning Toleration . Much of Locke’s work is characterized by opposition to authoritarianism. This is apparent both on the level of the individual person and on the level of institutions such as government and church. For the individual, Locke wants each of us to use reason to search after truth rather than simply accept the opinion of authorities or be subject to superstition. He wants us to proportion assent to propositions to the evidence for them. On the level of institutions it becomes important to distinguish the legitimate from the illegitimate functions of institutions and to make the corresponding distinction for the uses of force by these institutions. Locke believes that using reason to try to grasp the truth, and determine the legitimate functions of institutions will optimize human flourishing for the individual and society both in respect to its material and spiritual welfare. This in turn, amounts to following natural law and the fulfillment of the divine purpose for humanity.

1.1 Locke’s Life up to His Meeting with Lord Ashley in 1666

1.2 locke and lord shaftesbury 1666 to 1688, 1.3 the end of locke’s life 1689–1704, 2.2 book ii, 2.3 book iii, 2.4 book iv, 2.5 knowledge and probability, 2.6 reason, faith and enthusiasm, 3. locke’s major works on education, 4.1 the second treatise of government, 4.2 human nature and god’s purposes, 4.3 of war and slavery, 4.4 of property, 4.5 the social contract theory, 4.6 the function of civil government, 4.7 rebellion and regicide, 5. locke and religious toleration, primary sources, secondary sources, other internet resources, related entries, 1. historical background and locke’s life.

John Locke (1632–1704) was one of the greatest philosophers in Europe at the end of the seventeenth century. Locke grew up and lived through one of the most extraordinary centuries of English political and intellectual history. It was a century in which conflicts between Crown and Parliament and the overlapping conflicts between Protestants, Anglicans and Catholics swirled into civil war in the 1640s. With the defeat and death of Charles I, there began a great experiment in governmental institutions including the abolishment of the monarchy, the House of Lords and the Anglican church, and the establishment of Oliver Cromwell’s Protectorate in the 1650s. The collapse of the Protectorate after the death of Cromwell was followed by the Restoration of Charles II—the return of the monarchy, the House of Lords and the Anglican Church. This period lasted from 1660 to 1688. It was marked by continued conflicts between King and Parliament and debates over religious toleration for Protestant dissenters and Catholics. This period ends with the Glorious Revolution of 1688 in which James II was driven from England and replaced by William of Orange and his wife Mary. The final period during which Locke lived involved the consolidation of power by William and Mary, and the beginning of William’s efforts to oppose the domination of Europe by the France of Louis XIV, which later culminated in the military victories of John Churchill—the Duke of Marlborough.

Locke was born in Wrington to Puritan parents of modest means. His father was a country lawyer who served in a cavalry company on the Puritan side in the early stages of the English Civil War. His father’s commander, Alexander Popham, became the local MP, and it was his patronage which allowed the young John Locke to gain an excellent education. In 1647 Locke went to Westminster School in London.

From Westminster school he went to Christ Church, Oxford, in the autumn of 1652 at the age of twenty. As Westminster school was the most important English school, so Christ Church was the most important Oxford college. Education at Oxford was medieval. Locke, like Hobbes before him, found the Aristotelian philosophy he was taught at Oxford of little use. There was, however, more at Oxford than Aristotle. The new experimental philosophy had arrived. John Wilkins, Cromwell’s brother in law, had become Warden of Wadham College. The group around Wilkins was the nucleus of what was to become the English Royal Society. The Society grew out of informal meetings and discussion groups and moved to London after the Restoration and became a formal institution in the 1660s with charters from Charles II. The Society saw its aims in contrast with the Scholastic/Aristotelian traditions that dominated the universities. The program was to study nature rather than books. [ 1 ] Many of Wilkins associates were people interested in pursuing medicine by observation rather than the reading of classic texts. Bacon’s interest in careful experimentation and the systematic collection of facts from which generalizations could be made was characteristic of this group. One of Locke’s friends from Westminster school, Richard Lower, introduced Locke to medicine and the experimental philosophy being pursued by the virtuosi at Wadham.

Locke received his B.A. in February 1656. His career at Oxford, however, continued beyond his undergraduate days. In June of 1658, Locke qualified as a Master of Arts and was elected a Senior Student of Christ Church College. The rank was equivalent to a Fellow at any of the other colleges, but was not permanent. Locke had yet to determine what his career was to be. Locke was elected Lecturer in Greek at Christ Church in December of 1660 and he was elected Lecturer in Rhetoric in 1663. At this point, Locke needed to make a decision. The statutes of Christ Church laid it down that fifty five of the senior studentships should be reserved for men in orders or reading for orders. Only five could be held by others, two in medicine, two in law and one in moral philosophy. Thus, there was good reason for Locke to become a clergyman. Since his graduation Locke had been studying medicine. Locke decided to become a doctor.

John Wilkins had left Oxford with the Restoration of Charles II. The new leader of the Oxford scientific group was Robert Boyle. He was also Locke’s scientific mentor. Boyle (with the help of his astonishing assistant Robert Hooke) built an air pump which led to the formulation of Boyle’s law and devised a barometer as a weather indicator. The work on the air pump led to a controversy with Thomas Hobbes because Boyle’s explanations of the working of the air pump were incompatible with Hobbes’ micro-corpuscular theory. This controversy continued for ten years. Boyle was, however, most influential as a theorist. He was a mechanical philosopher who treated the world as reducible to matter in motion. But he had no micro-corpuscular account of the air.

Locke read Boyle before he read Descartes. When he did read Descartes, he saw the great French philosopher as providing a viable alternative to the sterile Aristotelianism he had been taught at Oxford. In writing An Essay Concerning Human Understanding Locke adopted Descartes’ ‘way of ideas’; though it is transformed so as to become an organic part of Locke’s philosophy. Still, while admiring Descartes, Locke’s involvement with the Oxford scientists gave him a perspective that made him critical of the rationalist elements in Descartes’ philosophy.

In the Epistle to the Reader at the beginning of the Essay Locke remarks:

The commonwealth of learning is not at this time without master-builders, whose mighty designs, in advancing the sciences, will leave lasting monuments to the admiration of posterity: but everyone must not hope to be a Boyle or a Sydenham; and in an age that produces such masters as the great Huygenius and the incomparable Mr. Newton, with some others of that strain, it is ambition enough to be employed as an under-labourer in clearing the ground a little, and removing some of the rubbish that lies in the way to knowledge …. (N: 9–10; all quotations are from the Nidditch edition of An Essay Concerning Human Understanding [N])

Locke knew all of these men and their work. Locke, Boyle and Newton were all founding or early members of the English Royal Society. It is from Boyle that Locke learned about atomism (or the corpuscular hypothesis) and it is from Boyle’s book The Origin of Forms and Qualities that Locke took the language of primary and secondary qualities. Sydenham was an English physician and Locke did medical research with him. Sydenham championed careful observation of disease and rejected appeal to underlying causes. Both Boyle and Newton did work on colors that did not involve micro-corpuscular explanations. Locke read Newton’s Principia Mathematica Philosophiae Naturalis while in exile in Holland, and consulted Huygens as to the soundness of its mathematics. Locke and Newton became friends after Locke’s return from Holland in 1688. It may be that in referring to himself as an ‘under-labourer’, Locke is not only displaying a certain literary modesty, he is contrasting the positive discoveries of these men, with his own attempt to show the inadequacies of the Aristotelian and Scholastic and to some degree the Cartesian philosophies. There are, however, many aspects of Locke’s project to which this image of an under-labourer does not do justice (see Jolley 1999: 15–17). While the corpuscular philosophy and Newton’s discoveries clearly influenced Locke, it is the Baconian program of producing natural histories that Locke makes reference to when he talks about the Essay in the Introduction. He writes:

It shall suffice to my present Purpose, to consider the discerning Faculties of a Man, as they are employ’d about the Objects, which they have to do with: and I shall imagine that I have not wholly misimploy’d my self in the Thoughts I shall have on this Occasion, if in this Historical, Plain Method, I can give any Account of the Ways, whereby our Understanding comes to attain those Notions of Things, and can set down any Measure of the Certainty of our Knowledge…. (I.1.2, N: 43–4—the three numbers, are book, chapter and section numbers respectively, followed by the page number in the Nidditch edition)

The ‘Historical, Plain Method’ is apparently to give a genetic account of how we come by our ideas. Presumably this will reveal the degree of certainty of the knowledge based on such ideas. Locke’s own active involvement with the scientific movement was largely through his informal studies of medicine. Dr. David Thomas was his friend and collaborator. Locke and Thomas had a laboratory in Oxford which was very likely, in effect, a pharmacy. In 1666 Lord Ashley, one of the richest men in England, came to Oxford in order to drink some medicinal waters there. He had asked Dr. Thomas to provide them. Thomas had to be out of town and asked Locke to see that the water was delivered. As a result of this encounter, Ashley invited Locke to come to London as his personal physician. In 1667 Locke did move to London becoming not only Lord Ashley’s personal physician, but secretary, researcher, political operative and friend. Living with him Locke found himself at the very heart of English politics in the 1670s and 1680s.

Locke’s chief work while living at Lord Ashley’s residence, Exeter House, in 1668 was as Ashley’s physician. Locke used his medical training to organize a successful operation on Ashley. This was perhaps the most carefully documented operation in the 17th century. Locke consulted doctors across the country to determine what the best practices were for this operation and made cleanliness a priority. In doing so he saved his patron’s life and thus changed English history.

Locke had a number of other jobs. He worked as secretary of the Board of Trade and Plantations and Secretary to the Lords Proprietors of the Carolinas. Lord Ashley was one of the advocates of the view that England would prosper through trade and that colonies could play an important role in promoting trade. Ashley persuaded Charles II to create a Board of Trade and Plantations to collect information about trade and colonies, and Locke became its secretary. In his capacity as the secretary of the Board of Trade Locke was the collection point for information from around the globe about trade and colonies for the English government. Among Ashley’s commercial projects was an effort to found colonies in the Carolinas. In his capacity as the secretary to the Lords Proprietors, Locke was involved in the writing of the fundamental constitution of the Carolinas. There is some controversy about the extent of Locke’s role in writing the constitution. [ 2 ] In addition to issues about trade and colonies, Locke was involved through Shaftesbury in other controversies about public policy. There was a monetary crisis in England involving the value of money, and the clipping of coins. Locke wrote papers for Lord Ashley on economic matters, including the coinage crisis.

While living in London at Exeter House, Locke continued to be involved in philosophical discussions. He tells us that:

Were it fit to trouble thee with the history of this Essay, I should tell thee, that five or six friends meeting at my chamber, and discoursing on a subject very remote from this, found themselves quickly at a stand, by the difficulties that rose on every side. After we had awhile puzzled ourselves, without coming any nearer a resolution of those doubts which perplexed us, it came into my thoughts that we took a wrong course; and that before we set ourselves upon inquiries of that nature, it was necessary to examine our own abilities, and see what objects our understandings were, or were not, fitted to deal with. This I proposed to the company, who all readily assented; and thereupon it was agreed that this should be our first inquiry. Some hasty and undigested thoughts, on a subject I had never before considered, which I set down against our next meeting, gave the first entrance into this Discourse; which having been thus begun by chance, was continued by intreaty; written by incoherent parcels; and after long intervals of neglect, resumed again, as my humour or occasions permitted; and at last, in a retirement where an attendance on my health gave me leisure, it was brought into that order thou now seest it. (Epistle to the Reader, N: 7)

James Tyrrell, one of Locke’s friends was at that meeting. He recalls the discussion being about the principles of morality and revealed religion (Cranston 1957: 140–1). Thus the Oxford scholar and medical researcher came to begin the work which was to occupy him off and on over the next twenty years.

In 1674 after Shaftesbury had left the government, Locke went back to Oxford, where he acquired the degree Bachelor of medicine, and a license to practice medicine, and then went to France (Cranston 1957: 160). In France Locke went from Calais to Paris, Lyons and on to Montpellier, where he spent the next fifteen months. Much of Locke’s time was spent learning about Protestantism in France. The Edict of Nantes (promulgated by Henry IV in 1598) was in force, and so there was a degree of religious toleration in France. Louis XIV was to revoke the edict in 1685 and French Protestants were then killed while some 400,000 went into exile.

While Locke was in France, Shaftesbury’s fortunes fluctuated. In 1676 Shaftesbury was imprisoned in the tower. His imprisonment lasted for a year. In 1678, after the mysterious murder of a London judge, informers (most notably Titus Oates) started coming forward to reveal a supposed Catholic conspiracy to assassinate the King and put his brother on the throne. This whipped up public anti-Catholic frenzy. Though Shaftesbury had not fabricated the conspiracy story, nor did he prompt Oates to come forward, he did exploit the situation to the advantage of his party. In the public chaos surrounding the sensational revelations, Shaftesbury organized an extensive party network, exercised great control over elections, and built up a large parliamentary majority. His strategy was to secure the passage of an Exclusion bill that would prevent Charles II’s openly Catholic brother from becoming King. Although the Exclusion bill passed in the Commons it was rejected in the House of Lords because of the King’s strong opposition to it. As the panic over the Popish plot receded, Shaftesbury was left without a following or a cause. Shaftesbury was seized on July 21, 1681 and again put in the tower. He was tried on trumped-up charges of treason but acquitted by a London grand jury (filled with his supporters) in November.

At this point some of the Country Party leaders began plotting an armed insurrection which, had it come off, would have begun with the assassination of Charles and his brother on their way back to London from the races at Newmarket. The chances of such a rising occurring were not as good as the plotters supposed. Memories of the turmoil of the civil war were still relatively fresh. Eventually Shaftesbury, who was moving from safe house to safe house, gave up and fled to Holland in November 1682. He died there in January 1683. Locke stayed in England until the Rye House Plot (named after the house from which the plotters were to fire upon the King and his brother) was discovered in June of 1683. Locke left for the West country to put his affairs in order the very week the plot was revealed to the government and by September he was in exile in Holland. [ 3 ]

While in exile, Locke finished An Essay Concerning Human Understanding and published a fifty-page advanced notice of it in French. (This was to provide the intellectual world on the continent with most of their information about the Essay until Pierre Coste’s French translation appeared in 1704.) He also wrote and published his Epistola de Tolerentia in Latin. Richard Ashcraft, in his Revolutionary Politics and Locke’s Two Treatises of Government (1986) suggests that while in Holland, Locke was not only finishing An Essay Concerning Human Understanding and nursing his health, he was closely associated with the English revolutionaries in exile. The English government was much concerned with this group. They tried to get a number of them, including Locke, extradited to England. Locke’s studentship at Oxford was taken away from him. In the meanwhile, the English intelligence service infiltrated the rebel group in Holland and effectively thwarted their efforts—at least for a while. While Locke was living in exile in Holland, Charles II died on Feb. 6, 1685, and was succeeded by his brother, who became James II of England. Soon after this, the rebels in Holland sent a force of soldiers under the Duke of Monmouth to England to try to overthrow James II. The revolt was crushed, and Monmouth was captured and executed (Ashcraft 1986). For a meticulous, if cautious review, of the evidence concerning Locke’s involvement with the English rebels in exile see Roger Woolhouse’s Locke: A Biography (2007).

Ultimately, however, the rebels were successful. James II alienated most of his supporters, and William of Orange was invited to bring a Dutch force to England. After William’s army landed, James II, realizing that he could not mount an effective resistance, fled the country to exile in France. This became known as the Glorious Revolution of 1688. It is a watershed in English history. For it marks the point at which the balance of power in the English government passed from the King to the Parliament. Locke returned to England in February 1689.

After his return from exile, Locke published An Essay Concerning Human Understanding and The Two Treatises of Government . In addition, Popple’s translation of Locke’s A Letter Concerning Toleration was also published. It is worth noting that the Two Treatises and the Letter Concerning Toleration were published anonymously. Locke took up residence in the country at Oates in Essex, the home of Sir Francis and Lady Masham (Damaris Cudworth). Locke had met Damaris Cudworth in 1682 and became involved intellectually and romantically with her. She was the daughter of Ralph Cudworth, the Cambridge Platonist, and a philosopher in her own right. After Locke went into exile in Holland in 1683, she married Sir Francis Masham. Locke and Lady Masham remained good friends and intellectual companions to the end of Locke’s life. During the remaining years of his life, Locke oversaw four more editions of the Essay and engaged in controversies over the Essay most notably in a series of published letters with Edward Stillingfleet, Bishop of Worcester. In a similar way, Locke defended the Letter Concerning Toleration against a series of attacks. He wrote The Reasonableness of Christianity and Some Thoughts on Education during this period as well.

Nor was Locke finished with public affairs. In 1696 the Board of Trade was revived. Locke played an important part in its revival and served as the most influential member on it until 1700. The new Board of Trade had administrative powers and was, in fact, concerned with a wide range of issues, from the Irish wool trade and the suppression of piracy, to the treatment of the poor in England and the governance of the colonies. It was, in Peter Laslett’s phrase “the body which administered the United States before the American Revolution” (Laslett 1954 [1990: 127]). During these last eight years of his life, Locke was asthmatic, and he suffered so much from it that he could only bear the smoke of London during the four warmer months of the year. Locke plainly engaged in the activities of the Board out of a strong sense of patriotic duty. After his retirement from the Board of Trade in 1700, Locke remained in retirement at Oates until his death on Sunday 28 October 1704.

2. The Limits of Human Understanding

Locke is often classified as the first of the great English empiricists (ignoring the claims of Bacon and Hobbes). This reputation rests on Locke’s greatest work, the monumental An Essay Concerning Human Understanding . Locke explains his project in several places. Perhaps the most important of his goals is to determine the limits of human understanding. Locke writes:

For I thought that the first Step towards satisfying the several Enquiries, the Mind of Man was apt to run into, was, to take a Survey of our own Understandings, examine our own Powers, and see to what Things they were adapted. Till that was done, I suspected that we began at the wrong end, and in vain sought for Satisfaction in a quiet and secure Possession of Truths, that most concern’d us whilst we let loose our Thoughts into the vast Ocean of Being , as if all the boundless Extent, were the natural and undoubted Possessions of our Understandings, wherein there was nothing that escaped its Decisions, or that escaped its Comprehension. Thus Men, extending their Enquiries beyond their Capacities, and letting their Thoughts wander into those depths where they can find no sure Footing; ’tis no Wonder, that they raise Questions and multiply Disputes, which never coming to any clear Resolution, are proper to only continue and increase their Doubts, and to confirm them at last in a perfect Skepticism. Wheras were the Capacities of our Understanding well considered, the Extent of our Knowledge once discovered, and the Horizon found, which sets the boundary between the enlightened and the dark Parts of Things; between what is and what is not comprehensible by us, Men would perhaps with less scruple acquiesce in the avow’d Ignorance of the one; and employ their Thoughts and Discourse, with more Advantage and Satisfaction in the other. (I.1.7, N: 47)

Some philosophers before Locke had suggested that it would be good to find the limits of the Understanding, but what Locke does is to carry out this project in detail. In the four books of the Essay Locke considers the sources and nature of human knowledge. Book I argues that we have no innate knowledge. (In this he resembles Berkeley and Hume, and differs from Descartes and Leibniz.) So, at birth, the human mind is a sort of blank slate on which experience writes. In Book II Locke claims that ideas are the materials of knowledge and all ideas come from experience. The term ‘idea’, Locke tells us “…stands for whatsoever is the Object of the Understanding, when a man thinks” (I.1.8, N: 47). Experience is of two kinds, sensation and reflection. One of these—sensation—tells us about things and processes in the external world. The other—reflection—tells us about the operations of our own minds. Reflection is a sort of internal sense that makes us conscious of the mental processes we are engaged in. Some ideas we get only from sensation, some only from reflection and some from both.

Locke has an atomic or perhaps more accurately a corpuscular theory of ideas. [ 4 ] There is, that is to say, an analogy between the way atoms or corpuscles combine into complexes to form physical objects and the way ideas combine. Ideas are either simple or complex. We cannot create simple ideas, we can only get them from experience. In this respect the mind is passive. Once the mind has a store of simple ideas, it can combine them into complex ideas of a variety of kinds. In this respect the mind is active. Thus, Locke subscribes to a version of the empiricist axiom that there is nothing in the intellect that was not previously in the senses—where the senses are broadened to include reflection. Book III deals with the nature of language, its connections with ideas and its role in knowledge. Book IV, the culmination of the previous reflections, explains the nature and limits of knowledge, probability, and the relation of reason and faith. Let us now consider the Essay in some detail.

At the beginning of An Essay Concerning Human Understanding Locke says that since his purpose is “to enquire into the Original, Certainty and Extent of human knowledge, together with the grounds and degrees of Belief, Opinion and Assent” he is going to begin with ideas—the materials out of which knowledge is constructed. His first task is to “enquire into the Original of these Ideas…and the ways whereby the Understanding comes to be furnished with them” (I.1.3, N: 44). The role of Book I of the Essay is to make the case that being innate is not a way in which the understanding is furnished with principles and ideas. Locke treats innateness as an empirical hypothesis and argues that there is no good evidence to support it.

Locke describes innate ideas as “some primary notions…Characters as it were stamped upon the Mind of Man, which the Soul receives in its very first Being; and brings into the world with it” (I.2.1, N: 48). In pursuing this enquiry, Locke rejects the claim that there are speculative innate principles (I.2), practical innate moral principles (I.3) or that we have innate ideas of God, identity or impossibility (I.4). Locke rejects arguments from universal assent and attacks dispositional accounts of innate principles. Thus, in considering what would count as evidence from universal assent to such propositions as “What is, is” or “It is impossible for the same thing to be and not to be” he holds that children and idiots should be aware of such truths if they were innate but that they “have not the least apprehension or thought of them”. Why should children and idiots be aware of and able to articulate such propositions? Locke says:

It seems to me a near Contradiction to say that there are truths imprinted on the Soul, which it perceives or understands not; imprinting if it signify anything, being nothing else but the making certain Truths to be perceived. (I.2.5, N: 49)

So, Locke’s first point is that if propositions were innate they should be immediately perceived—by infants and idiots (and indeed everyone else)—but there is no evidence that they are. Locke then proceeds to attack dispositional accounts that say, roughly, that innate propositions are capable of being perceived under certain circumstances. Until these circumstances come about the propositions remain unperceived in the mind. With the advent of these conditions, the propositions are then perceived. Locke gives the following argument against innate propositions being dispositional:

For if any one [proposition] may [be in the mind but not be known]; then, by the same Reason, all Propositions that are true, and the Mind is ever capable of assenting to, may be said to be in the Mind, and to be imprinted: since if any one can be said to be in the Mind, which it never yet knew, it must be only because it is capable of knowing it; and so the Mind is of all Truths it ever shall know. (I.2.5, N: 50)

The essence of this argument and many of Locke’s other arguments against dispositional accounts of innate propositions is that such dispositional accounts do not provide an adequate criterion for distinguishing innate propositions from other propositions that the mind may come to discover. Thus, even if some criterion is proposed, it will turn out not to do the work it is supposed to do.

When Locke turns from speculative principles to the question of whether there are innate practical moral principles, many of the arguments against innate speculative principles continue to apply, but there are some additional considerations. Practical principles, such as the Golden Rule, are not self-evident in the way such speculative principles as “What is, is” are. Thus, one can clearly and sensibly ask reasons for why one should hold the Golden Rule true or obey it (I.3.4, N: 68). There are substantial differences between people over the content of practical principles. Thus, they are even less likely candidates to be innate propositions or to meet the criterion of universal assent. In the fourth chapter of Book I, Locke raises similar points about the ideas which compose both speculative and practical principles. The point is that if the ideas that are constitutive of the principles are not innate, this gives us even more reason to hold that the principles are not innate. He examines the ideas of identity, impossibility and God to make these points.

In Book I Locke says little about who holds the doctrine of innate principles that he is attacking. For this reason he has sometimes been accused of attacking straw men. John Yolton has persuasively argued (Yolton 1956) that the view that innate ideas and principles were necessary for the stability of religion, morality and natural law was widespread in England in the seventeenth century, and that in attacking both the naive and the dispositional account of innate ideas and innate principles, Locke is attacking positions which were widely held and continued to be held after the publication of the Essay . Thus, the charge that Locke’s account of innate principles is made of straw, is not a just criticism. But there are also some important connections with particular philosophers and schools that are worth noting and some points about innate ideas and inquiry.

At I. 4. 24. Locke tells us that the doctrine of innate principles once accepted “eased the lazy from the pains of search” and that the doctrine is an inquiry stopper that is used by those who “affected to be Masters and Teachers” to illegitimately gain control of the minds of their students. Locke rather clearly has in mind the Aristotelians and scholastics at the universities. Thus Locke’s attack on innate principles is connected with his anti-authoritarianism. It is an expression of his view of the importance of free and autonomous inquiry in the search for truth. Ultimately, Locke holds, this is the best road to knowledge and happiness. Locke, like Descartes, is tearing down the foundations of the old Aristotelian scholastic house of knowledge. But while Descartes focused on the empiricism at the foundation of the structure, Locke is focusing on the claims that innate ideas provide its first principles. The attack on innate ideas is thus the first step in the demolition of the scholastic model of science and knowledge. Ironically, it is also clear from II.1.9. that Locke sees Descartes’ claim that his essence is to be a thinking thing as entailing a doctrine of innate ideas and principles.

In Book II of the Essay , Locke gives his positive account of how we acquire the materials of knowledge. Locke distinguishes a variety of different kinds of ideas in Book II. Locke holds that the mind is a tabula rasa or blank sheet until experience in the form of sensation and reflection provide the basic materials—simple ideas—out of which most of our more complex knowledge is constructed. While the mind may be a blank slate in regard to content, it is plain that Locke thinks we are born with a variety of faculties to receive and abilities to manipulate or process the content once we acquire it. Thus, for example, the mind can engage in three different types of action in putting simple ideas together. The first of these kinds of action is to combine them into complex ideas. Complex ideas are of two kinds, ideas of substances and ideas of modes. Substances are independent existences. Beings that count as substances include God, angels, humans, animals, plants and a variety of constructed things. Modes are dependent existences. These include mathematical and moral ideas, and all the conventional language of religion, politics and culture. The second action which the mind performs is the bringing of two ideas, whether simple or complex, by one another so as to take a view of them at once, without uniting them. This gives us our ideas of relations (II.12.1, N: 163). The third act of the mind is the production of our general ideas by abstraction from particulars, leaving out the particular circumstances of time and place, which would limit the application of an idea to a particular individual. In addition to these abilities, there are such faculties as memory which allow for the storing of ideas.

Having set forth the general machinery of how simple and complex ideas of substances, modes, relations, and so forth are derived from sensation and reflection, Locke also explains how a variety of particular kinds of ideas, such as the ideas of solidity, number, space, time, power, identity, and moral relations arise from sensation and reflection. Several of these are of particular interest. Locke’s chapter on power gives rise to a discussion of free will and voluntary action (see the entry on Locke on freedom ). Locke also made a number of interesting claims in the philosophy of mind. He suggested, for example, that for all we know, God could as easily add the powers of perception and thought to matter organized in the right way as he could add those powers to an immaterial substance which would then be joined to matter organized in the right way. His account of personal identity in II. xxvii was revolutionary. (See the entry on Locke on personal identity) . Both of these topics and related ones are treated in the supplementary document: Some Interesting Issues in Locke’s Philosophy of Mind

In what follows, we focus on some central issues in Locke’s account of physical objects. (See also the entry Locke’s philosophy of science , which pursues a number of topics related to Locke’s account of physical objects that are of considerable importance but largely beyond the scope of this general account of Locke’s philosophy.) These include Locke on knowledge in natural philosophy, the limitations of the corpuscular philosophy and Locke’s relation to Newton.

Locke offers an account of physical objects based on the mechanical philosophy and the corpuscular hypothesis. The adherents of the mechanical philosophy held that all material phenomena can be explained by matter in motion and the impact of one body on another. They viewed matter as passive. They rejected the “occult qualities” and “causation at a distance” of the Aristotelian and Scholastic philosophy. Robert Boyle’s corpuscularian hypothesis treated the material world as made up of particles. Some corpuscularians held that corpuscles could be further divided and that the universe was full of matter with no void space. Atomists, on the other hand, held that the particles were indivisible and that the material world is composed of atoms and the void or empty space in which the atoms move. Locke was an atomist.

Atoms have properties. They are extended, they are solid, they have a particular shape and they are in motion or rest. They combine together to produce the familiar stuff and physical objects, the gold and the wood, the horses and violets, the tables and chairs of our world. These familiar things also have properties. They are extended, solid, have a particular shape, and are in motion and at rest. In addition to these properties that they share with the atoms that compose them, they have other properties such as colors, smells, tastes that they get by standing in relation to perceivers. The distinction between these two kinds of properties goes back to the Greek atomists. It is articulated by Galileo and Descartes as well as Locke’s mentor Robert Boyle.

Locke makes this distinction in Book II Chapter 8 of the Essay and using Boyle’s terminology calls the two different classes of properties the primary and secondary qualities of an object. This distinction is made by both of the main branches of the mechanical philosophy of the seventeenth and early eighteenth century. Both the Cartesian plenum theorists, who held that the world was full of infinitely divisible matter and that there was no void space, and the atomists such as Gassendi, who held that there were indivisible atoms and void space in which the atoms move, made the distinction between these two classes of properties. Still, the differences between these two branches of the mechanical philosophy affect their account of primary qualities. In the chapter on Solidity (II.4) Locke rejects the Cartesian definition of body as simply extended and argues that bodies are both extended and impenetrable or solid. The inclusion of solidity in Locke’s account of bodies and of primary qualities distinguishes them from the void space in which they move.

The primary qualities of an object are properties which the object possesses independent of us—such as occupying space, being either in motion or at rest, having solidity and texture. The secondary qualities are powers in bodies to produce ideas in us like color, taste, smell and so on that are caused by the interaction of our particular perceptual apparatus with the primary qualities of the object. Our ideas of primary qualities resemble the qualities in the object, while our ideas of secondary qualities do not resemble the powers that cause them. Locke also distinguishes a second class of secondary properties that are the powers that one substance has to effect another, e.g. the power of a fire to melt a piece of wax.

There has been considerable scholarly debate concerning the details of Locke’s account of the distinction. Among the issues are which qualities Locke assigns to each of the two categories. Locke gives several lists. Another issue is what the criterion is for putting a quality in one list rather than another. Does Locke hold that all the ideas of secondary qualities come to us by one sense while the ideas of primary qualities come to us through two or is Locke not making the distinction in this way? Another issue is whether there are only primary qualities of atoms or whether compounds of atoms also have primary qualities. And while Locke claims our ideas of primary qualities resemble the primary qualities in objects, and the ideas of secondary qualities do not resemble their causes in the object, what does ‘resemble’ mean in this context? Related to this issue is how we are supposed to know about particles that we cannot sense. It seems clear that Locke holds that there are certain analogies between the middle sized macroscopic objects we encounter in the world, e.g. porphyry and manna for example, and the particles that compose these things. Maurice Mandelbaum called this process ‘transdiction’. These analogies allow us to say certain things about the nature of particles and primary and secondary qualities. For example we can infer that atoms are solid and that heat is a greater rate of motion of atoms while cold is a slower motion. But these analogies may not get us very far in grasping the necessary connections between qualities in nature. Yet another issue is whether Locke sees the distinction as reductionistic. If what we mean by reductionistic here is that only the primary qualities are real and these explain the secondary qualities then there does not seem to be a clear answer. Secondary qualities surely are nothing more than certain primary qualities that affect us in certain ways. This seems to be reductionistic. But on Locke’s account of “real ideas” in II.30 both the ideas of primary and secondary qualities count as real. And while Locke holds that our ideas of secondary qualities are caused by primary qualities, in certain important respects the primary qualities do not explain them. Locke holds that we cannot even conceive how the size, figure and motion of particles could cause any sensation in us. So, knowing the size, figure and motion of the particles would be of no use to us in this regard (see IV.3.11–40, N: 544–546).

Locke probably holds some version of the representational theory of perception, though some scholars dispute this. On such a theory what the mind immediately perceives are ideas, and the ideas are caused by and represent the objects which cause them. Thus perception is a triadic relation, rather than simply being a dyadic relation between an object and a perceiver. Such a dyadic relational theory is often called naive realism because it suggests that the perceiver is directly perceiving the object, and naive because this view is open to a variety of serious objections. Some versions of the representational theory are open to serious objections as well. If, for example, one treats ideas as things, then one can imagine that because one sees ideas, the ideas actually block one from seeing things in the external world. The idea would be like a picture or painting. The picture would copy the original object in the external world, but because our immediate object of perception is the picture we would be prevented from seeing the original just as standing in front of a painting on an easel might prevent us from seeing the person being painted. Thus, this is sometimes called the picture/original theory of perception. Alternatively, Jonathan Bennett called it “the veil of perception” to emphasize that ‘seeing’ the ideas prevents us from seeing the external world. One philosopher who arguably held such a view was Nicholas Malebranche, a follower of Descartes. Antoine Arnauld, by contrast, while believing in the representative character of ideas, is a direct realist about perception. Arnauld engaged in a lengthy controversy with Malebranche, and criticized Malebranche’s account of ideas. Locke follows Arnauld in his criticism of Malebranche on this point (Locke, 1823, Vol. IX: 250). Yet Berkeley attributed the veil of perception interpretation of the representational theory of perception to Locke as have many later commentators including Bennett. A.D. Woozley puts the difficulty of doing this succinctly:

…it is scarcely credible both that Locke should be able to see and state so clearly the fundamental objection to the picture-original theory of sense perception, and that he should have held the same theory himself. (Woozley 1964: 27)

Just what Locke’s account of perception involves, is still a matter of scholarly debate. A review of this issue at a symposium including John Rogers, Gideon Yaffe, Lex Newman, Tom Lennon, and Vere Chappell at a meeting of the Pacific Division of the American Philosophical Association in 2003 and later expanded and published in the Pacific Philosophical Quarterly (2004, volume 85, issue 3) found most of the symposiasts holding the view that Locke holds a representative theory of perception but that he is not a skeptic about the external world in the way that the veil of perception doctrine might suggest.

Another issue that has been a matter of controversy since the first publication of the Essay is what Locke means by the term ‘substance’. The primary/secondary quality distinction gets us a certain ways in understanding physical objects, but Locke is puzzled about what underlies or supports the primary qualities themselves. He is also puzzled about what material and immaterial substances might have in common that would lead us to apply the same word to both. These kinds of reflections led him to the relative and obscure idea of substance in general. This is an “I know not what” which is the support of qualities which cannot subsist by themselves. We experience properties appearing in regular clumps, but we must infer that there is something that supports or perhaps ‘holds together’ those qualities. For we have no experience of that supporting substance. It is clear that Locke sees no alternative to the claim that there are substances supporting qualities. He does not, for example, have a theory of tropes (tropes are properties that can exist independently of substances) which he might use to dispense with the notion of substance. (In fact, he may be rejecting something like a theory of tropes when he rejects the Aristotelian doctrine of real qualities and insists on the need for substances.) He is thus not at all a skeptic about ‘substance’ in the way that Hume is. But, it is also quite clear that he is regularly insistent about the limitations of our ideas of substances. Bishop Stillingfleet accused Locke of putting substance out of the reasonable part of the world. But Locke is not doing that.

Since Berkeley, Locke’s doctrine of the substratum or substance in general has been attacked as incoherent. It seems to imply that we have a particular without any properties, and this seems like a notion that is inconsistent with empiricism. We have no experience of such an entity and so no way to derive such an idea from experience. Locke himself acknowledges this point (I.4.18, N: 95). In order to avoid this problem, Michael Ayers has proposed that we must understand the notions of ‘substratum’ and ‘substance in general’ in terms of Locke’s distinction between real and nominal essences and particularly his doctrine of real essences developed in Book III of the Essay rather than as a separate problem from that of knowing real essences. The real essence of a material thing is its atomic constitution. This atomic constitution is the causal basis of all the observable properties of the thing, from which we create nominal essences. Were the real essence known, all the observable properties could be deduced from it. Locke claims that the real essences of material things are quite unknown to us. Locke’s concept of substance in general is also a ‘something I know not what’. Thus, on Ayers’ interpretation ‘substance in general’ means something like ‘whatever it is that supports qualities’ while the real essence means ‘this particular atomic constitution that explains this set of observable qualities’. Thus, Ayers wants to treat the unknown substratum as picking out the same thing as the real essence—thus eliminating the need for particulars without properties. This proposed way of interpreting Locke has been criticized by scholars both because of a lack of textural support, and on the stronger grounds that it conflicts with some things that Locke does say (see Jolley 1999: 71–3). As we have reached one of the important concepts in Book III, let us turn to that Book and Locke’s discussion of language.

Locke devotes Book III of An Essay Concerning Human Understanding to language. This is a strong indication that Locke thinks issues about language were of considerable importance in attaining knowledge. At the beginning of the Book he notes the importance of abstract general ideas to knowledge. These serve as sorts under which we rank all the vast multitude of particular existences. Thus, abstract ideas and classification are of central importance in Locke’s discussion of language and its importance for knowledge. Without general terms and classes we would be faced with the impossible task of trying to know a vast world of particulars.

There is a clear connection between Books II and III in that Locke claims that words stand for ideas. In his discussion of language Locke distinguishes words according to the categories of ideas established in Book II of the Essay . So there are ideas of substances, simple modes, mixed modes, relations and so on. It is in this context that Locke makes the distinction between real and nominal essences noted above. Perhaps because of his focus on the role that kind terms play in classification, Locke pays vastly more attention to nouns than to verbs. Locke recognizes that not all words relate to ideas. There are also the many particles, words that “…signify the connexion that the Mind gives to Ideas, or Propositions, one with another” (II.7.1, N: 471). Still, it is the relation of words and ideas that gets most of Locke’s attention in Book III.

Norman Kretzmann calls the claim that “words in their primary or immediate signification signify nothing but the ideas in the mind of him that uses them ” (III.2.2) “Locke’s main semantic thesis” (see Kretzmann 1968:179). This thesis has often been criticized as a classic blunder in semantic theory. Thus Mill, for example, wrote, “When I say, ‘the sun is the cause of the day’, I do not mean that my idea of the sun causes or excites in me the idea of day” (Mill 1843: bk 1, ch. 2, § 1). This criticism of Locke’s account of language parallels the “veil of perception” critique of his account of perception and suggests that Locke is not distinguishing the meaning of a word from its reference. Kretzmann, however, argues persuasively that Locke distinguishes between meaning and reference and that ideas provide the meaning but not the reference of words. Thus, the line of criticism represented by the quotation from Mill is ill founded.

In addition to the kinds of ideas noted above, there are also particular and abstract ideas. Particular ideas have in them the ideas of particular places and times which limit the application of the idea to a single individual, while abstract general ideas leave out the ideas of particular times and places in order to allow the idea to apply to other similar qualities or things. There has been considerable philosophical and scholarly debate about the nature of the process of abstraction and Locke’s account of it. Berkeley argued that the process as Locke conceives it is incoherent. In part this is because Berkeley is an imagist—that is he believes that all ideas are images. If one is an imagist it becomes impossible to imagine what idea could include both the ideas of a right and equilateral triangle. Michael Ayers has recently argued that Locke too was an imagist. This would make Berkeley’s criticism of Locke very much to the point. Ayers’ claim, however, has been disputed (see, for example, Soles 1999). The process of abstraction is of considerable importance to human knowledge. Locke thinks most words we use are general (III.1.1, N: 409). Clearly, it is only general or sortal ideas that can serve in a classificatory scheme.

In his discussion of names of substances and in the contrast between names of substances and names of modes, a number of interesting features of Locke’s views about language and knowledge emerge. Physical substances are atoms and things made up of atoms. But we have no experience of the atomic structure of horses and tables. We know horses and tables mainly by secondary qualities such as color, taste and smell and so on and primary qualities such as shape, motion and extension. So, since the real essence (the atomic constitution) of a horse is unknown to us, our word ‘horse’ cannot get its meaning from that real essence. What the general word signifies is the complex of ideas we have decided are parts of the idea of that sort of thing. These ideas we get from experience. Locke calls such a general idea that picks out a sort, the nominal essence of that sort.

One of the central issues in Book III has to do with classification. On what basis do we divide things into kinds and organize those kinds into a system of species and genera? In the Aristotelian and Scholastic tradition that Locke rejects, necessary properties are those that an individual must have in order to exist and continue to exist. These contrast with accidental properties. Accidental properties are those that an individual can gain and lose and yet continue in existence. If a set of necessary properties is shared by a number of individuals, that set of properties constitutes the essence of a natural kind. The borders between kinds are supposed to be sharp and determinate. The aim of Aristotelian science is to discover the essences of natural kinds. Kinds can then be organized hierarchically into a classificatory system of species and genera. This classification of the world by natural kinds will be unique and privileged because it alone corresponds to the structure of the world. This doctrine of essences and kinds is often called Aristotelian essentialism. Locke rejects a variety of aspects of this doctrine. He rejects the notion that an individual has an essence apart from being treated as belonging to a kind. He also rejects the claim that there is a single classification of things in nature that the natural philosopher should seek to discover. He holds that there are many possible ways to classify the world each of which might be particularly useful depending on one’s purposes.

Locke’s pragmatic account of language and the distinction between nominal and real essences constitute an anti-essentialist alternative to this Aristotelian essentialism and its correlative account of the classification of natural kinds. He claims that there are no fixed boundaries in nature to be discovered—that is there are no clear demarcation points between species. There are always borderline cases. There is debate over whether Locke’s view is that this lack of fixed boundaries is true on both the level of appearances and nominal essences, and atomic constitutions and real essences, or on the level of nominal essences alone. The first view is that Locke holds that there are no Aristotelian natural kinds on either the level of appearance or atomic reality. The second view holds that Locke thinks there are Aristotelian natural kinds on the atomic level, it is simply that we cannot get at them or know what they are. On either of these interpretations, the real essence cannot provide the meaning to names of substances. A.O. Lovejoy in the Great Chain of Being , and David Wiggins are proponents of the second interpretation while Michael Ayers and William Uzgalis argue for the first (Uzgalis 1988; Ayers 1991: II. 70).

By contrast, the ideas that we use to make up our nominal essences come to us from experience. Locke claims that the mind is active in making our ideas of sorts and that there are so many properties to choose among that it is possible for different people to make quite different ideas of the essence of a certain substance. This has given some commentators the impression that the making of sorts is utterly arbitrary and conventional for Locke and that there is no basis for criticizing a particular nominal essence. Sometimes Locke says things that might suggest this. But this impression should be resisted. Peter Anstey has characterized Locke’s conventionalism about classificatory terms as both constrained and convergent (Anstey 2011: 209, 212). Locke claims that while the making of nominal essences is the work of the understanding, that work is constrained both by usage (where words stand for ideas that are already in use) and by the fact that substance words are supposed to copy the properties of the substances they refer to. Locke says that our ideas of kinds of substances have as their archetype the complex of properties that produce the appearances we use to make our nominal essences and which cause the unity of the complex of ideas that appear to us regularly conjoined. The very notion of an archetype implies constraints on what properties (and hence what ideas) can go together. If there were no such constraints there could be no archetype. (For further discussion of the nominal-real essence distinction see the entry Locke on Real Essences) .

Let us begin with the usage of words. It is important in a community of language users that words be used with the same meaning. If this condition is met it facilitates the chief end of language which is communication. If one fails to use words with the meaning that most people attach to them, one will fail to communicate effectively with others. Thus one would defeat the main purpose of language. It should also be noted that traditions of usage for Locke can be modified. Otherwise we would not be able to improve our knowledge and understanding by getting more clear and determinate ideas.

In the making of the names of substances, there is a period of discovery as the abstract general idea is put together (e.g. the discovery of violets or gold) and then the naming of that idea and then its introduction into language. Language itself is viewed as an instrument for carrying out the mainly prosaic purposes and practices of everyday life. Ordinary people are the chief makers of language.

Vulgar Notions suit vulgar Discourses; and both though confused enough, yet serve pretty well for the Market and the Wake. Merchants and Lovers, Cooks and Taylors, have Words wherewith to dispatch their ordinary affairs; and so, I think, might Philosophers and Disputants too, if they had a mind to understand and to be clearly understood. (III.11.10, N: 514)

These ordinary people use a few apparent qualities, mainly ideas of secondary qualities to make ideas and words that will serve their purposes.

Natural philosophers (i.e. scientists) come along later to try to determine if the connections between properties which the ordinary folk have put together in a particular idea in fact holds in nature. Scientists are seeking to find the necessary connections between properties. Still, even scientists, in Locke’s view, are restricted to using observable (and mainly secondary) qualities to categorize things in nature. Sometimes, the scientists may find that the ordinary folk had erred, as when they called whales ‘fish’. A whale is not a fish, as it turns out, but a mammal. There is a characteristic group of qualities that fish have that whales do not have. There is a characteristic group of qualities that mammals have that whales also have. To classify a whale as a fish, therefore, is a mistake. Similarly, we might make an idea of gold that only included being a soft metal and gold color. If so, we would be unable to distinguish between gold and fool’s gold. Thus, since it is the mind that makes complex ideas (they are ‘the workmanship of the understanding’), one is free to put together any combination of ideas one wishes and call it what one will. But the product of such work is open to criticism, either on the grounds that it does not conform to already current usage or that it inadequately represents the archetypes that it is supposed to copy in the world. We engage in such criticism in order to improve human understanding of the material world and thus the human condition. This is the convergent character of Locke’s conventionalism. In becoming more accurate, the nominal essence converges on the real essence.

However, we should not forget the master-builders that Locke mentions at the beginning of the Essay . Stephen Gaukroger (2010) claims that Locke’s great achievement was to provide a philosophical justification for the kind of experimental philosophy that Boyle’s work on the air pump, and his and Newton’s work on colors, as well as Sydenham’s observational medicine. All of these had been attacked for not providing explanations in terms of matter theory. Thus, Locke is justifying the autonomy of experimental philosophy. Such experimental explanations depend solely on the relation between phenomena, even when there is some micro-corpuscular basis for the phenomena being explained. According to Gaukroger, this is Locke’s contribution to the collapse of mechanism. For the details of the problem and its solution, see Chapters 4 and 5 of Gaukroger (2010).

The distinction between modes and substances is surely one of the most important in Locke’s philosophy. In contrast with substances, modes are dependent existences—they can be thought of as the ordering of substances. These are technical terms for Locke, so we should see how they are defined. Locke writes:

First, Modes I call such complex Ideas , which however compounded, contain not in themselves the supposition of subsisting by themselves; such are the ideas signified by the Words Triangle, Gratitude, Murther, etc . (II.12.4, N: 165)

Locke goes on to distinguish between simple and mixed modes. He writes:

Of these Modes , there are two sorts, which deserve distinct consideration. First, there are some that are only variations, or different combinations of the same simple Idea , without the mixture of any other, as a dozen or score; which are nothing but the ideas of so many distinct unities being added together, and these I call simple Modes , as being contained within the bounds of one simple Idea . Secondly, There are others, compounded of Ideas of several kinds, put together to make one complex one; v.g. Beauty , consisting of a certain combination of Colour and Figure, causing Delight to the Beholder; Theft , which being the concealed change of the Possession of any thing, without the consent of the Proprietor, contains, as is visible, a combination of several Ideas of several kinds; and these I call Mixed Modes . (II.12.5, N: 165)

When we make ideas of modes, the mind is again active, but the archetype is in our mind. The question becomes whether things in the world fit our ideas, and not whether our ideas correspond to the nature of things in the world. Our ideas are adequate. Thus we define ‘bachelor’ as an unmarried, adult, male human being. If we find that someone does not fit this definition, this does not reflect badly on our definition, it simply means that that individual does not belong to the class of bachelors. Modes give us the ideas of mathematics, of morality, of religion and politics and indeed of human conventions in general. Since these modal ideas are not only made by us but serve as standards that things in the world either fit or do not fit and thus belong or do not belong to that sort, ideas of modes are clear and distinct, adequate and complete. Thus in modes, we get the real and nominal essences combined. One can give precise definitions of mathematical terms (that is, give necessary and sufficient conditions), and one can give deductive demonstrations of mathematical truths. Locke sometimes says that morality too is capable of deductive demonstration. Though pressed by his friend William Molyneux to produce such a demonstrative morality, Locke never did so. The entry Locke’s moral philosophy provides an excellent discussion of Locke’s views on morality and issues related to them for which there is no room in this general account. The terms of political discourse also have some of the same modal features for Locke. When Locke defines the states of nature, slavery, and war in the Second Treatise of Government , for example, we are presumably getting precise modal definitions from which one can deduce consequences. It is possible, however, that with politics we are getting a study that requires both experience as well as the deductive modal aspect.

In the fourth book of An Essay Concerning Human Understanding Locke tells us what knowledge is and what humans can know and what they cannot (not simply what they do and do not happen to know). Locke defines knowledge as “the perception of the connexion and agreement or disagreement and repugnancy of any of our Ideas” (IV.1.1, N: 525). This definition of knowledge contrasts with the Cartesian definition of knowledge as any ideas that are clear and distinct. Locke’s account of knowledge allows him to say that we can know substances in spite of the fact that our ideas of them always include the obscure and relative idea of substance in general. Still, Locke’s definition of knowledge raises in this domain a problem analogous to those we have seen with perception and language. If knowledge is the “perception of … the agreement or disagreement … of any of our Ideas”—are we not trapped in the circle of our own ideas? What about knowing the real existence of things? Locke is plainly aware of this problem, and very likely holds that the implausibility of skeptical hypotheses, such as Descartes’ Dream hypothesis (he doesn’t even bother to mention Descartes’ malin genie or Evil Demon hypothesis), along with the causal connections between qualities and ideas in his own system is enough to solve the problem. It is also worth noting that there are significant differences between Locke’s brand of empiricism and that of Berkeley that would make it easier for Locke to solve the veil of perception problem than Berkeley. Locke, for example, makes transdictive inferences about atoms where Berkeley is unwilling to allow that such inferences are legitimate. This implies that Locke has a semantics that allows him to talk about the unexperienced causes of experience (such as atoms) where Berkeley cannot. (See Mackie’s perceptive discussion of the veil of perception problem, in Problems from Locke , 1976: 51 through 67.)

What then can we know and with what degree of certainty? We can know that God exists with the second highest degree of assurance, that of demonstration. We also know that we exist with the highest degree of certainty. The truths of morality and mathematics we can know with certainty as well, because these are modal ideas whose adequacy is guaranteed by the fact that we make such ideas as ideal models which other things must fit, rather than trying to copy some external archetype which we can only grasp inadequately. On the other hand, our efforts to grasp the nature of external objects are limited largely to the connection between their apparent qualities. The real essence of elephants and gold is hidden from us: though in general we suppose them to be some distinct combination of atoms which cause the grouping of apparent qualities which leads us to see elephants and violets, gold and lead as distinct kinds. Our knowledge of material things is probabilistic and thus opinion rather than knowledge. Thus our “knowledge” of external objects is inferior to our knowledge of mathematics and morality, of ourselves, and of God. We do have sensitive knowledge of external objects, which is limited to things we are presently experiencing. While Locke holds that we only have knowledge of a limited number of things, he thinks we can judge the truth or falsity of many propositions in addition to those we can legitimately claim to know. This brings us to a discussion of probability.

Knowledge involves the seeing of the agreement or disagreement of our ideas. What then is probability and how does it relate to knowledge? Locke writes:

The Understanding Faculties being given to Man, not barely for Speculation, but also for the Conduct of his Life, Man would be at a great loss, if he had nothing to direct him, but what has the Certainty of true Knowledge … Therefore, as God has set some Things in broad day-light; as he has given us some certain Knowledge…So in the greater part of our Concernment, he has afforded us only the twilight, as I may say so, of Probability, suitable, I presume, to that State of Mediocrity and Probationership, he has been pleased to place us in here, wherein to check our over-confidence and presumption, we might by every day’s Experience be made sensible of our short sightedness and liableness to Error… (IV.14.1–2, N: 652)

So, apart from the few important things that we can know for certain, e.g. the existence of ourselves and God, the nature of mathematics and morality broadly construed, for the most part we must lead our lives without knowledge. What then is probability? Locke writes:

As Demonstration is the shewing of the agreement or disagreement of two Ideas, by the intervention of one or more Proofs, which have a constant, immutable, and visible connexion one with another: so Probability is nothing but the appearance of such an Agreement or Disagreement, by the intervention of Proofs, whose connection is not constant and immutable, or at least is not perceived to be so, but is or appears, for the most part to be so, and is enough to induce the Mind to judge the Proposition to be true, or false, rather than the contrary. (IV.15.1, N: 654)

Probable reasoning, on this account, is an argument, similar in certain ways to the demonstrative reasoning that produces knowledge but different also in certain crucial respects. It is an argument that provides evidence that leads the mind to judge a proposition true or false but without a guarantee that the judgment is correct. This kind of probable judgment comes in degrees, ranging from near demonstrations and certainty to unlikeliness and improbability in the vicinity of impossibility. It is correlated with degrees of assent ranging from full assurance down to conjecture, doubt and distrust.

The new science of mathematical probability had come into being on the continent just around the time that Locke was writing the Essay . His account of probability, however, shows little or no awareness of mathematical probability. Rather it reflects an older tradition that treated testimony as probable reasoning. Given that Locke’s aim, above all, is to discuss what degree of assent we should give to various religious propositions, the older conception of probability very likely serves his purposes best. Thus, when Locke comes to describe the grounds for probability he cites the conformity of the proposition to our knowledge, observation and experience, and the testimony of others who are reporting their observation and experience. Concerning the latter we must consider the number of witnesses, their integrity, their skill in observation, counter testimony and so on. In judging rationally how much to assent to a probable proposition, these are the relevant considerations that the mind should review. We should, Locke also suggests, be tolerant of differing opinions as we have more reason to retain the opinions we have than to give them up to strangers or adversaries who may well have some interest in our doing so.

Locke distinguishes two sorts of probable propositions. The first of these have to do with particular existences or matters of fact, and the second that are beyond the testimony of the senses. Matters of fact are open to observation and experience, and so all of the tests noted above for determining rational assent to propositions about them are available to us. Things are quite otherwise with matters that are beyond the testimony of the senses. These include the knowledge of finite immaterial spirits such as angels or things such as atoms that are too small to be sensed, or the plants, animals or inhabitants of other planets that are beyond our range of sensation because of their distance from us. Concerning this latter category, Locke says we must depend on analogy as the only help for our reasoning. He writes:

Thus the observing that the bare rubbing of two bodies violently one upon the other, produce heat, and very often fire it self, we have reason to think, that what we call Heat and Fire consist of the violent agitation of the imperceptible minute parts of the burning matter…. (IV.16.12, N: 665–6)

We reason about angels by considering the Great Chain of Being; figuring that while we have no experience of angels, the ranks of species above us is likely as numerous as that below of which we do have experience. This reasoning is, however, only probable.

The relative merits of the senses, reason and faith for attaining truth and the guidance of life were a significant issue during this period. As noted above James Tyrrell recalled that the original impetus for the writing of An Essay Concerning Human Understanding was a discussion about the principles of morality and revealed religion. In Book IV Chapters 17, 18, and 19 Locke deals with the nature of reason, the relation of reason to faith and the nature of enthusiasm. Locke remarks that all sects make use of reason as far as they can. It is only when this fails them that they have recourse to faith and claim that what is revealed is above reason. But he adds:

And I do not see how they can argue with anyone or even convince a gainsayer who uses the same plea, without setting down strict boundaries between faith and reason. (IV.18.2, N: 689)

Locke then defines reason as

the discovery of the certainty or probability of such propositions or truths, which the mind arrives at by deduction made from such ideas, as it has got by the use of its natural faculties; viz, by the use of sensation or reflection. (IV.18.2, N: 689)

Faith, on the other hand, is assent to any proposition “…upon the credit of the proposer, as coming from God, in some extraordinary way of communication”. That is we have faith in what is disclosed by revelation and which cannot be discovered by reason. Locke also distinguishes between the original revelation by God to some person, and traditional revelation which is the original revelation “…delivered over to others in Words, and the ordinary ways of our conveying our Conceptions one to another” (IV.18.3, N: 690).

Locke makes the point that some things could be discovered both by reason and by revelation—God could reveal the propositions of Euclid’s geometry, or they could be discovered by reason. In such cases there would be little use for faith. Traditional revelation can never produce as much certainty as the contemplation of the agreement or disagreement of our own ideas. Similarly revelations about matters of fact do not produce as much certainty as having the experience oneself. Revelation, then, cannot contradict what we know to be true. If it could, it would undermine the trustworthiness of all of our faculties. This would be a disastrous result. Where revelation comes into its own is where reason cannot reach. Where we have few or no ideas for reason to contradict or confirm, these are the proper matters for faith.

…that Part of the Angels rebelled against GOD, and thereby lost their first happy state: and that the dead shall rise, and live again: These and the like, being Beyond the Discovery of Reason, are purely matters of Faith; with which Reason has nothing to do. (IV.18.8, N: 694)

Still, reason does have a crucial role to play in respect to revelation. Locke writes:

Because the Mind, not being certain of the Truth of that it evidently does not know, but only yielding to the Probability that appears to it, is bound to give up its assent to such Testimony, which, it is satisfied, comes from one who cannot err, and will not deceive. But yet, it still belongs to Reason, to judge of the truth of its being a Revelation, and of the significance of the Words, wherein it is delivered. (IV.18.8, N: 694)

So, in respect to the crucial question of how we are to know whether a revelation is genuine, we are supposed to use reason and the canons of probability to judge. Locke claims that if the boundaries between faith and reason are not clearly marked, then there will be no place for reason in religion and one then gets all the “extravagant Opinions and Ceremonies, that are to be found in the religions of the world…” (IV.18.11, N: 696).

Should one accept revelation without using reason to judge whether it is genuine revelation or not, one gets what Locke calls a third principle of assent besides reason and revelation, namely enthusiasm. Enthusiasm is a vain or unfounded confidence in divine favor or communication. It implies that there is no need to use reason to judge whether such favor or communication is genuine or not. Clearly when such communications are not genuine they are “the ungrounded Fancies of a Man’s own Brain” (IV.19.2, N: 698). This kind of enthusiasm was characteristic of Protestant extremists going back to the era of the civil war. Locke was not alone in rejecting enthusiasm, but he rejects it in the strongest terms. Enthusiasm violates the fundamental principle by which the understanding operates—that assent be proportioned to the evidence. To abandon that fundamental principle would be catastrophic. This is a point that Locke also makes in The Conduct of the Understanding and The Reasonableness of Christianity . Locke wants each of us to use our understanding to search after truth. Of enthusiasts, those who would abandon reason and claim to know on the basis of faith alone, Locke writes:

…he that takes away Reason to make way for Revelation, puts out the Light of both, and does much what the same, as if he would perswade a Man to put out his eyes, the better to receive the remote Light of an invisible Star by a Telescope. (IV.19.4, N: 698)

Rather than engage in the tedious labor required to reason correctly to judge of the genuineness of their revelation, enthusiasts persuade themselves that they are possessed of immediate revelation. This leads to “odd Opinions and extravagant actions” that are characteristic of enthusiasm and which should warn that this is a wrong principle. Thus, Locke strongly rejects any attempt to make inward persuasion not judged by reason a legitimate principle.

We turn now to a consideration of Locke’s educational works.

Locke’s Some Thoughts Concerning Education and his Conduct of the Understanding form a nice bridge between An Essay Concerning Human Understanding and his political works. Ruth Grant and Nathan Tarcov write in the introduction to their edition of these works:

The idea of liberty, so crucial to all of Locke’s writings on politics and education, is traced in the Essay to reflection on the power of the mind over one’s own actions, especially the power to suspend actions in the pursuit of the satisfaction of one’s own desires until after a full consideration of their objects (II.21.47, N: 51–52). The Essay thus shows how the independence of mind pursued in the Conduct is possible. (G&T 1996: xvi)

Some Thoughts Concerning Education was first published in 1693. This book collected together advice that Locke had been giving his friend Edward Clarke about the education of Clarke’s son (and also his daughters) since 1684. In preparing the revision for the fourth edition of An Essay Concerning Human Understanding Locke began writing a chapter called “The Conduct of the Understanding”. This became quite long and was never added to the Essay or even finished. It was left to Locke’s literary executors to decide what to do with it. The Conduct was published by Peter King in his posthumous edition of some of Locke’s works in 1706. As Locke was composing these works, some of the material from the Conduct eventually made its way into the Thoughts . Grant and Tarcov write that the Thoughts and the Conduct “complement each other well: the Thoughts focuses on the education of children by their parents, whereas the Conduct addresses the self-education of adults” (G&T 1996: vii). Though they also note tensions between the two that illustrate paradoxes in liberal society. The Thoughts is addressed to the education of the sons and daughters of the English gentry in the late seventeenth century. It is in some ways thus significantly more limited to its time and place than the Conduct . Yet, its insistence on the inculcating such virtues as

justice as respect for the rights of others, civility, liberality, humanity, self-denial, industry, thrift, courage, truthfulness, and a willingness to question prejudice, authority and the biases of one’s own self-interest

very likely represents the qualities needed for citizens in a liberal society (G&T 1996: xiii).

Locke’s Thoughts represents the culmination of a century of what has been called “the discovery of the child”. In the Middle Ages the child was regarded as

only a simple plaything, as a simple animal, or a miniature adult who dressed, played and was supposed to act like his elders…Their ages were unimportant and therefore seldom known. Their education was undifferentiated, either by age, ability or intended occupation. (Axtell 1968: 63–4)

Locke treated children as human beings in whom the gradual development of rationality needed to be fostered by parents. Locke urged parents to spend time with their children and tailor their education to their character and idiosyncrasies, to develop both a sound body and character, and to make play the chief strategy for learning rather than rote learning or punishment. Thus, he urged learning languages by learning to converse in them before learning rules of grammar. Locke also suggests that the child learn at least one manual trade.

In advocating a kind of education that made people who think for themselves, Locke was preparing people to effectively make decisions in their own lives—to engage in individual self-government—and to participate in the government of their country. The Conduct reveals the connections Locke sees between reason, freedom and morality. Reason is required for good self-government because reason insofar as it is free from partiality, intolerance and passion and able to question authority leads to fair judgment and action. We thus have a responsibility to cultivate reason in order to avoid the moral failings of passion, partiality and so forth (G&T 1996: xii). This is, in Tarcov’s phrase, Locke’s education for liberty.

We turn now to Locke’s political writings. (See the entry on Locke’s political philosophy , which focuses on five topics (the state of nature, natural law, property, consent and toleration) and goes into these topics in more depth than is possible in a general account and provides much useful information on the debates about them.)

4. The Two Treatises Of Government

Lord Shaftsbury had been dismissed from his post as Lord Chancellor in 1673 and had become one of the leaders of the opposition party, the Country Party. In 1679 the chief issue was the attempt by the Country Party leaders to exclude James, Duke of York from succeeding his brother Charles II to the throne. They wanted to do this because James was a Catholic, and England by this time was a firmly Protestant country. They had acquired a majority in the House of Commons through serious grass roots election campaigns, and passed an exclusion bill, but given the King’s unwillingness to see his brother excluded from the throne, the bill failed in the House of Lords. They tried a couple of more times without success. Having failed by parliamentary means, some of the Country Party leaders started plotting armed rebellion.

The Two Treatises of Government were published in 1689, long after the rebellion plotted by the Country party leaders had failed to materialize and after Shaftsbury had fled the country for Holland and died. The introduction of the Two Treatises was written after the Glorious Revolution of 1688, and gave the impression that the book was written to justify the Glorious Revolution. We now know that the Two Treatises of Government were written during the Exclusion crisis in 1681 and may have been intended in part to justify the general armed rising which the Country Party leaders were planning.

There were serious obstacles to a rebellion to force James’ exclusion from the throne. The English Anglican gentry needed to support such an action. But the Anglican church from childhood on taught that: “…men’s political duties were exhaustively determined by their terrestrial superiors, that under grave conscientious scruples they might rightly decline to carry out those decrees of authority which were in direct breach of divine law, they could under no circumstances have a right to resist such authority”. (Dunn, 1968, 48) Since by 1679 it was abundantly clear that the King opposed excluding his brother from the throne, to favor exclusion implied “explicit and self-conscious resistance to the sovereign”. Passive resistance would simply not do. On the other hand, the royal policy “outraged their deepest religious prejudices and stimulated their most obscure emotional anxieties.” So, the gentry were deeply conflicted and neither of the choices available to them looked very palatable. John Dunn goes on to remark: “To exert influence upon their choice it was above all necessary to present a more coherent ordering of their values, to show that the political tradition within which the dissenters saw their conduct was not necessarily empirically absurd or socially subversive. The gentry had to be persuaded that there could be reason for rebellion which could make it neither blasphemous or suicidal.” (Dunn, 1968, 49) To achieve this goal Locke picked the most relevant and extreme of the supporters of the divine right of Kings to attack. Sir Robert Filmer (c 1588–1653), a man of the generation of Charles I and the English Civil War, who had defended the crown in various works. His most famous work, however, Patriarcha , was published posthumously in 1680 and represented the most complete and coherent exposition of the view Locke wished to deny. Filmer held that men were born into helpless servitude to an authoritarian family, a social hierarchy and a sovereign whose only constraint was his relationship with God. Under these circumstances, anything other than passive obedience would be “vicious, blasphemous and intellectually absurd.” So, Locke needed to refute Filmer and in Dunn’s words: “rescue the contractarian account of political obligation from the criticism of impiety and absurdity. Only in this way could he restore to the Anglican gentry a coherent basis for moral autonomy or a practical initiative in the field of politics.” (Dunn, 1968, 50)

The First Treatise of Government is a polemical work aimed at refuting the theological basis for the patriarchal version of the Divine Right of Kings doctrine put forth by Sir Robert Filmer. Locke singles out Filmer’s contention that men are not “naturally free” as the key issue, for that is the “ground” or premise on which Filmer erects his argument for the claim that all “legitimate” government is “absolute monarchy”—kings being descended from the first man, Adam, and their subjects being naturally slaves. Early in the First Treatise Locke denies that either scripture or reason supports Filmer’s premise or arguments. In what follows in the First Treatise , Locke minutely examines key Biblical passages.

While The Second Treatise of Government provides Locke’s positive theory of government, it also continues his argument against Sir Robert Filmer’s claims that monarchs legitimately hold absolute power over their subjects. Locke holds that Filmer’s view is sufficiently incoherent to lead to governments being established by force and violence. Thus, Locke claims he must provide an alternative account of the origin of government “lest men fall into the dangerous belief that all government in the world is merely the product of force and violence” ( Treatises II,1,4). Locke’s account involves several devices which were common in seventeenth and eighteenth century political philosophy—natural rights theory and the social contract. Natural rights are those rights which we are supposed to have as human beings before ever government comes into being. We might suppose, that like other animals, we have a natural right to struggle for our survival. Locke will argue that we have a right to the means to survive. When Locke comes to explain how government comes into being, he uses the idea that people agree that their condition in the state of nature is unsatisfactory, and so agree to transfer some of their rights to a central government, while retaining others. This is the theory of the social contract. There are many versions of natural rights theory and the social contract in seventeenth and eighteenth century European political philosophy, some conservative and some radical. Locke’s version belongs on the radical side of the spectrum. These radical natural right theories influenced the ideologies of the American and French revolutions.

Locke’s strategy for refuting Filmer’s claims that monarchs have absolute power over their subjects is to show that Filmer is conflating a whole variety of limited powers, all of which might be held by one man and thus give the false appearance that a king has absolute power over wives, children, servants and slaves as well as subjects of a commonwealth. When properly distinguished, however, and the limitations of each displayed, it becomes clear that monarchs have no legitimate absolute power over their subjects.

An important part of Locke’s project in the Second Treatise is to figure out what the role of legitimate government is, thus allowing him to distinguish the nature of illegitimate government. Once this is done, the basis for legitimate revolution becomes clear. Figuring out what the proper or legitimate role of civil government is would be a difficult task indeed if one were to examine the vast complexity of existing governments. How should one proceed? One strategy is to consider what life is like in the absence of civil government. Presumably this is a simpler state, one which may be easier to understand. Then one might see what role civil government ought to play. This is the strategy which Locke pursues, following Hobbes and others. So, in the first chapter of the Second Treatise Locke defines political power.

Political power , then, I take to be a right of making laws with penalties of death, and consequently all less penalties, for the regulating and preserving of property, and of employing the force of the community, in the execution of such laws, and in the defence of the common-wealth from foreign injury; and all this only for the public good. ( Treatises, II, 1,3)

In the second chapter of The Second Treatise Locke describes the state in which there is no government with real political power. This is the state of nature. It is sometimes assumed that the state of nature is a state in which there is no government at all. This is only partially true. It is possible to have in the state of nature either no government, illegitimate government, or legitimate government with less than full political power. (See the section on the state of nature in the entry on Locke’s political philosophy.)

If we consider the state of nature before there was government, it is a state of political equality in which there is no natural superior or inferior. From this equality flows the obligation to mutual love and the duties that people owe one another, and the great maxims of justice and charity. Was there ever such a state? There has been considerable debate about this. Still, it is plain that both Hobbes and Locke would answer this question affirmatively. Whenever people have not agreed to establish a common political authority, they remain in the state of nature. It’s like saying that people are in the state of being naturally single until they are married. Locke clearly thinks one can find the state of nature in his time at least in the “inland, vacant places of America” ( Second Treatise V. 36) and in the relations between different peoples. Perhaps the historical development of states also went though the stages of a state of nature. An alternative possibility is that the state of nature is not a real historical state, but rather a theoretical construct, intended to help determine the proper function of government. If one rejects the historicity of states of nature, one may still find them a useful analytical device. For Locke, it is very likely both.

According to Locke, God created man and we are, in effect, God’s property. The chief end set us by our creator as a species and as individuals is survival. A wise and omnipotent God, having made people and sent them into this world:

…by his order and about his business, they are his property whose workmanship they are, made to last during his, not one another’s pleasure: and being furnished with like faculties, sharing all in one community of nature, there cannot be supposed any subordination among us, that may authorize us to destroy one another, as if we were made for one another’s uses, as the inferior ranks of creatures are for our’s. ( Treatises II,2,6)

It follows immediately that “he has no liberty to destroy himself, or so much as any creature in his possession, yet when some nobler use than its bare possession calls for it” ( Treatises II.2.6). So, murder and suicide violate the divine purpose.

If one takes survival as the end, then we may ask what are the means necessary to that end. On Locke’s account, these turn out to be life, liberty, health and property. Since the end is set by God, on Locke’s view we have a right to the means to that end. So we have rights to life, liberty, health and property. These are natural rights, that is they are rights that we have in a state of nature before the introduction of civil government, and all people have these rights equally.

There is also a law of nature. It is the Golden Rule, interpreted in terms of natural rights. Thus Locke writes:

The state of nature has a law of nature to govern it, which obliges everyone: and reason which is that law, teaches all mankind who will but consult it, that being all equal and independent, no one ought to harm another in his life, health, liberty or possessions…. ( Treatises II.2.6)

Locke tells us that the law of nature is revealed by reason. Locke makes the point about the law that it commands what is best for us. If it did not, he says, the law would vanish for it would not be obeyed. It is in this sense that Locke means that reason reveals the law. If you reflect on what is best for yourself and others, given the goal of survival and our natural equality, you will come to this conclusion. (See the section on the law of nature in the entry on Locke’s Political Philosophy.)

Locke does not intend his account of the state of nature as a sort of utopia. Rather it serves as an analytical device that explains why it becomes necessary to introduce civil government and what the legitimate function of civil government is. Thus, as Locke conceives it, there are problems with life in the state of nature. The law of nature, like civil laws can be violated. There are no police, prosecutors or judges in the state of nature as these are all representatives of a government with full political power. The victims, then, must enforce the law of nature in the state of nature. In addition to our other rights in the state of nature, we have the rights to enforce the law and to judge on our own behalf. We may, Locke tells us, help one another. We may intervene in cases where our own interests are not directly under threat to help enforce the law of nature. This right eventually serves as the justification for legitimate rebellion. Still, in the state of nature, the person who is most likely to enforce the law under these circumstances is the person who has been wronged. The basic principle of justice is that the punishment should be proportionate to the crime. But when the victims are judging the seriousness of the crime, they are more likely to judge it of greater severity than might an impartial judge. As a result, there will be regular miscarriages of justice. This is perhaps the most important problem with the state of nature.

In chapters 3 and 4, Locke defines the states of war and slavery. The state of war is a state in which someone has a sedate and settled intention of violating someone’s right to life (and thus all their other rights). Such a person puts themselves into a state of war with the person whose life they intend to take. In such a war the person who intends to violate someone’s right to life is an unjust aggressor. This is not the normal relationship between people enjoined by the law of nature in the state of nature. Locke is distancing himself from Hobbes who had made the state of nature and the state of war equivalent terms. For Locke, the state of nature is ordinarily one in which we follow the Golden Rule interpreted in terms of natural rights, and thus love our fellow human creatures. The state of war only comes about when someone proposes to violate someone else’s rights. Thus, on Locke’s theory of war, there will always be an innocent victim on one side and an unjust aggressor on the other.

Slavery is the state of being in the absolute or arbitrary power of another. On Locke’s definition of slavery, there is only one rather remarkable way to become a legitimate slave. In order to do so, one must be an unjust aggressor defeated in war. The just victor then has the option to either kill the aggressor or enslave them. Locke tells us that the state of slavery is the continuation of the state of war between a lawful conqueror and a captive, in which the conqueror delays taking the life of the captive, and instead makes use of him. This is a continued war because if conqueror and captive make some compact for obedience on the one side and limited power on the other, the state of slavery ceases and becomes a relation between a master and a servant in which the master only has limited power over his servant. The reason that slavery ceases with the compact is that “no man, can, by agreement pass over to another that which he hath not in himself, a power over his own life” ( Treatises II.4.24). Legitimate slavery is an important concept in Locke’s political philosophy largely because it tells us what the legitimate extent of despotic power is and defines and illuminates by contrast the nature of illegitimate slavery. Illegitimate slavery is that state in which someone possesses absolute or despotic power over someone else without just cause. Locke holds that it is this illegitimate state of slavery which absolute monarchs wish to impose upon their subjects. It is very likely for this reason that legitimate slavery is so narrowly defined. This shows that the chapter on slavery plays a crucial role in Locke’s argument against Sir Robert Filmer and thus could not have been easily dispensed with. Still, it is possible that Locke had an additional purpose or perhaps a quite different reason for writing about slavery.

There has been a steady stream of articles and books over the last sixty years arguing that given Locke’s involvement with trade and colonial government, the theory of slavery in the Second Treatise was intended to justify the institutions and practices of Afro-American slavery. If this were the case, Locke’s philosophy would not contradict his actions as an investor and colonial administrator. However, there are strong objections to this view. Had he intended to justify Afro-American slavery, Locke would have done much better with a vastly more inclusive definition of legitimate slavery than the one he gives. It is sometimes suggested that Locke’s account of “just war” is so vague that it could easily be twisted to justify the institutions and practices of Afro-American slavery. This, however, is also not the case. In the chapter “Of Conquest” Locke explicitly lists the limits of the legitimate power of conquerors. These limits on who can become a legitimate slave and what the powers of a just conqueror are ensure that this theory of conquest and slavery would condemn the institutions and practices of Afro-American slavery in the seventeenth, eighteenth, and nineteenth centuries. Nonetheless, the debate continues. One element of the debate has to do with Locke’s role in the writing of the Fundamental Constitutions of the Carolinas . David Armitage in his 2004 article “John Locke, Carolina and the Two Treatises of Government” argues that Locke was involved in a revision of the Fundamental Constitution of the Carolinas at the very time he was writing The Two Treatises of Government . The provision that “Every Freedman of the Carolinas has absolute power and authority over his negro slaves” remained in the document unchanged. In his 2016 book The Ashley Cooper Plan , Thomas Wilson gives a detailed account of Ashley Cooper’s intentions for the Carolina colony and how Cooper’s intent was thwarted by Barbadian slave owners who changed Carolina society from a society with slaves to a slave society. L. H. Roper, in his 2004 book Conceiving Carolina: Property, Planters and Plots 1662–1729 , offers a different account of what went wrong, focusing on conflicts over the trade in Indian slaves. James Farr’s article “Locke, Natural Law and New World Slavery” (2008) is one of the best statements of the position that Locke intended his theory of slavery to apply to English absolutism and not Afro-American slavery while noting that Locke’s involvement with slavery has ruined his reputation as the great champion of liberty Roger Woolhouse in his recent biography of Locke (Woolhouse 2007: 187) remarks that “Though there is no consensus on the whole question, there certainly seems to be ‘a glaring contradiction between his theories and Afro-American slavery’”.

Recently, there has been a debate over whose theory of slavery and absolutism Locke was attacking. Johan Olsthoorn and Laurens van Apeldoorn (2020) argue that Locke’s account of slavery and in particular, that no person can consensually establish absolute rule over themselves with all its consequences has little force against other classical contract theories, in particular those of Grotius and Puffendorf. Both Grotius and Puffendorf defended both absolutism and colonial slavery.

Felis Waldmann in “Slavery and Absolutism in Locke’s Two Treatises: A Response to Olsthoorn and van Apeldoorn” objects to a number of their claims finding others not relevant. Most notably, he objects to these claims: First, “Locke is working with an idiosyncratic conception of slavery and absolute rule repudiated by prominent early modern thinkers defending political absolutism.” Second: “Like Filmer, Locke maintains that absolute rulers may arbitrarily kill and maim their subjects at will, by dint of having a dominium in the latter’s lives.” Finally, he objects to the claim that: “Early modern natural lawyers, from Grotius onward, conceptualized slavery rather differently, insisting that enslaved people were not owned in the way we own things (which may be destroyed at will)” (Waldmann 7).

In brief, Waldmann’s response to the first claim is that Filmer accurately represented the Royalist position in the late 1670s and early 1680s and so Locke’s account is not a straw man. Thus, Locke is attacking Filmer’s account of slavery and not some weak and extreme version of the argument for absolutism that no one held. Waldmann suggests that the second claim magnifies this tendency of the two authors’ portrayal of Locke’s argument as not responding to the standard arguments for absolutism. Thus, Olsthoorn and van Apeldoorn attribute Filmer’s position to Locke. Waldmann concludes that the claims of Olsthoorn and van Apeldoorn that since Locke’s position on slavery was significantly different from those of Grotius and Puffendorf, it had little force against them is, in fact, the case. But he thinks this is of little importance since Locke was not arguing against them. One suggestion he considers plausible is that Locke is aiming his argument against the possibility of self-enslavement at Thomas Hobbes. Hobbes was recognized by his contemporaries as asserting both that one could by contract enslave oneself and that the king had dominium, over his subjects.

William Uzgalis, in his 2017 chapter “John Locke, Slavery and Indian Lands,” holds that Locke has two theories of slavery, one of them of legitimate slavery and the other of illegitimate slavery. Note that the authors discussed above simply don’t make this distinction. If they had, it would be plain that while Locke shares with Filmer the dominium conception of slavery that allows a master to kill or maim a slave, neither theory belongs to Filmer, and if Locke is correct about royal absolutism and given the character of the practices of the slave trade and colonial slavery, both absolutism at home and the slave trade and colonial slavery fall under the theory of illegitimate slavery. Neither Grotius, Puffendorf or Hobbes has an explicit theory of illegitimate slavery. Uzgalis also notes that Grotius and Puffendorf provided claims that Locke could have adopted had he wished to justify the slave trade and slavery in the colonies. Still, he denies them all, and with good reason. He would have substantially weakened his argument against the kind of absolutism he attributed to Filmer and the Stuarts had he done so. This suggests that he was crafting an alternative theory and not arguing against its competitors, with the exception, perhaps, of Hobbes.

Holly Brewer in her 2017 article “Slavery, Sovereignty, and ‘Inheritable Blood’, Reconsidering John Locke and the Origins of American Slavery” argues for a different approach to these questions. She presents evidence that the Stuart kings, and Charles II and his brother James, Duke of York, in particular, were not just interested in absolute government at home; they actively promoted the Royal Africa Company, the slave trade and slavery in the colonies as it provided considerable amounts of money to the royal coffers. James was the Governor (the President) of the Royal Africa Company and Admiral of the English fleet. Lord Shaftesbury, Locke’s patron, was the sub-governor, and Locke assisted him. Using the fleet, James attacked and captured Dutch forts on the coast of Africa to make bases for the Royal Africa Company and deprive the Dutch of them. The Stuarts minted guinea coins to celebrate these efforts. After becoming King, James continued as Governor of the Royal Africa Company. Thus Brewer underlines the similarities and connections between the absolutism Locke objected to at home and the slave trade and slavery in the colonies. She argues that the spread of slavery needs to be understood as an English imperial policy and not something that occurred in different times and places unconnected with one another. She also claims that while Locke was a member of King William III’s Board of Trade in the waning years of the seventeenth century, he sought to undo Stuart policies concerning slavery in the colonies.

Chapter 5 “Of Property” is one of the most famous, influential and important chapters in the Second Treatise of Government . Indeed, some of the most controversial issues about the Second Treatise come from varying interpretations of it. In this chapter Locke, in effect, describes the evolution of the state of nature to the point where it becomes expedient for those in it to found a civil government. So, it is not only an account of the nature and origin of private property but leads up to the explanation of why civil government replaces the state of nature (see the section on property in the entry on Locke’s political philosophy).

In discussing the origin of private property Locke begins by noting that God gave the earth to all men in common. Thus there is a question about how private property comes to be. Locke finds it a serious difficulty. He points out, however, that we are supposed to make use of the earth “for the best advantage of life and convenience” ( Treatises II.5.25). What then is the means to appropriate property from the common store? Locke argues that private property does not come about by universal consent. If one had to go about and ask everyone if one could eat these berries, one would starve to death before getting everyone’s agreement. Locke holds that we have property in our own person. And the labor of our body and the work of our hands properly belong to us. So, when one picks up acorns or berries, they thereby belong to the person who picked them up. There has been some controversy about what Locke means by “labor”. Daniel Russell claims that for Locke, labor is a goal-directed activity that converts materials that might meet our needs into resources that actually do (Russell 2004). This interpretation of what Locke means by “labor” connects nicely with his claim that we have a natural law obligation first to preserve ourselves and then to help in the preservation and flourishing of others.

One might think that one could then acquire as much as one wished, but this is not the case. Locke introduces at least two important qualifications on how much property can be acquired. The first qualification has to do with waste. Locke writes:

As much as anyone can make use of to any advantage of life before it spoils, so much by his labor he may fix a property in; whatever is beyond this, is more than his share, and belongs to others. ( Treatises II.5.31)

Since originally, populations were small and resources great, living within the bounds set by reason, there would be little quarrel or contention over property, for a single man could make use of only a very small part of what was available.

Note that Locke has, thus far, been talking about hunting and gathering, and the kinds of limitations which reason imposes on the kind of property that hunters and gatherers hold. In the next section he turns to agriculture and the ownership of land and the kinds of limitations there are on that kind of property. In effect, we see the evolution of the state of nature from a hunter/gatherer kind of society to that of a farming and agricultural society. Once again it is labor which imposes limitations upon how much land can be enclosed. It is only as much as one can work. But there is an additional qualification. Locke says:

Nor was this appropriation of any parcel of land , by improving it, any prejudice to any other man, since there was still enough, and as good left; and more than the as yet unprovided could use. So that, in effect, there was never the less for others because of his inclosure for himself: for he that leaves as much as another can make use of, does as good as take nothing at all. No body could consider himself injured by the drinking of another man, though he took a good draught, who had a whole river of the same water left to quench his thirst: and the case of land and water, where there is enough, is perfectly the same. ( Treatises II.5.33)

The next stage in the evolution of the state of nature involves the introduction of money. Locke remarks that:

… before the desire of having more than one needed had altered the intrinsic value of things, which depends only on their usefulness to the life of man; or had agreed, that a little piece of yellow metal, which would keep without wasting or decay, should be worth a great piece of flesh, or a whole heap of corn; though men had a right to appropriate by their labor, each one of himself, as much of the things of nature, as he could use; yet this could not be much, nor to the prejudice of others, where the same plenty was left to those who would use the same industry. ( Treatises II.5.37)

So, before the introduction of money, there was a degree of economic equality imposed on mankind both by reason and the barter system. And men were largely confined to the satisfaction of their needs and conveniences. Most of the necessities of life are relatively short lived—berries, plums, venison and so forth. One could reasonably barter one’s berries for nuts which would last not weeks but perhaps a whole year. And says Locke:

…if he would give his nuts for a piece of metal, pleased with its color, or exchange his sheep for shells, or wool for a sparkling pebble or diamond, and keep those by him all his life, he invaded not the right of others, he might heap up as much of these durable things as he pleased; the exceeding of the bounds of his property not lying in the largeness of his possessions, but the perishing of anything uselessly in it. ( Treatises II.5.146)

The introduction of money is necessary for the differential increase in property, with resulting economic inequality. Without money there would be no point in going beyond the economic equality of the earlier stage. In a money economy, different degrees of industry could give men vastly different proportions.

This partage of things in an inequality of private possessions, men have made practicable out of the bounds of society, and without compact, only by putting a value on gold and silver, and tacitly agreeing to the use of money: for in governments, the laws regulate the rights of property, and the possession of land is determined by positive constitutions. ( Treatises II.5.50)

The implication is that it is the introduction of money, which causes inequality, which in turn multiplies the causes of quarrels and contentions and increased numbers of violations of the law of nature. This leads to the decision to create a civil government. Before turning to the institution of civil government, however, we should ask what happens to the qualifications on the acquisition of property after the advent of money? One answer proposed by C. B. Macpherson in The Political Theory of Possessive Individualism is that the qualifications are completely set aside, and we now have a system for the unlimited acquisition of private property. This does not seem to be correct. It seems plain, rather, that at least the non-spoilage qualification is satisfied, because money does not spoil. The other qualifications may be rendered somewhat irrelevant by the advent of the conventions about property adopted in civil society. This leaves open the question of whether Locke approved of these changes. Macpherson, who takes Locke to be a spokesman for a proto-capitalist system, sees Locke as advocating the unlimited acquisition of wealth. James Tully, on the other side, in A Discourse of Property holds that Locke sees the new conditions, the change in values and the economic inequality which arise as a result of the advent of money, as the fall of man. Tully sees Locke as a persistent and powerful critic of self-interest. This remarkable difference in interpretation has been a significant topic for debates among scholars over the last forty years. Though the Second Treatise of Government may leave this question difficult to determine, one might consider Locke’s remark in Some Thoughts Concerning Education that

Covetousness and the desire to having in our possession and our dominion more than we have need of, being the root of all evil, should be early and carefully weeded out and the contrary quality of being ready to impart to others inculcated. (G&T 1996: 81)

Let us then turn to the institution of civil government.

Just as natural rights and natural law theory had a fluorescence in the seventeenth and eighteenth century, so did the social contract theory. Why is Locke a social contract theorist? Is it merely that this was one prevailing way of thinking about government at the time which Locke blindly adopted? The answer is that there is something about Locke’s project which pushes him strongly in the direction of the social contract. One might hold that governments were originally instituted by force, and that no agreement was involved. Were Locke to adopt this view, he would be forced to go back on many of the things which are at the heart of his project in the Second Treatise , though cases like the Norman conquest force him to admit that citizens may come to accept a government that was originally forced on them. Remember that the Second Treatise provides Locke’s positive theory of government, and that he explicitly says that he must provide an alternative to the view

that all government in the world is merely the product of force and violence, and that men live together by no other rules than that of the beasts, where the strongest carries it … . ( Treatises II, 1, 4)

So, while Locke might admit that some governments come about through force or violence, he would be destroying the most central and vital distinction, that between legitimate and illegitimate civil government, if he admitted that legitimate government can come about in this way. So, for Locke, legitimate government is instituted by the explicit consent of those governed. (See the section on consent, political obligation, and the ends of government in the entry on Locke’s political philosophy.) Those who make this agreement transfer to the government their right of executing the law of nature and judging their own case. These are the powers which they give to the central government, and this is what makes the justice system of governments a legitimate function of such governments.

Ruth Grant has persuasively argued that the establishment of government is in effect a two step process. Universal consent is necessary to form a political community. Consent to join a community once given is binding and cannot be withdrawn. This makes political communities stable. Grant writes: “Having established that the membership in a community entails the obligation to abide by the will of the community, the question remains: Who rules?” (1987: 114–115). The answer to this question is determined by majority rule. The point is that universal consent is necessary to establish a political community, majority consent to answer the question who is to rule such a community. Universal consent and majority consent are thus different in kind, not just in degree. Grant writes:

Locke’s argument for the right of the majority is the theoretical ground for the distinction between duty to society and duty to government, the distinction that permits an argument for resistance without anarchy. When the designated government dissolves, men remain obligated to society acting through majority rule. (1987: 119)

It is entirely possible for the majority to confer the rule of the community on a king and his heirs, or a group of oligarchs or on a democratic assembly. Thus, the social contract is not inextricably linked to democracy. Still, a government of any kind must perform the legitimate function of a civil government.

Locke is now in a position to explain the function of a legitimate government and distinguish it from illegitimate government. The aim of such a legitimate government is to preserve, so far as possible, the rights to life, liberty, health and property of its citizens, and to prosecute and punish those of its citizens who violate the rights of others and to pursue the public good even where this may conflict with the rights of individuals. In doing this it provides something unavailable in the state of nature, an impartial judge to determine the severity of the crime, and to set a punishment proportionate to the crime. This is one of the main reasons why civil society is an improvement on the state of nature. An illegitimate government will fail to protect the rights to life, liberty, health and property of its subjects, and in the worst cases, such an illegitimate government will claim to be able to violate the rights of its subjects, that is it will claim to have despotic power over its subjects. Since Locke is arguing against the position of Sir Robert Filmer who held that patriarchal power and political power are the same, and that in effect these amount to despotic power, Locke is at pains to distinguish these three forms of power, and to show that they are not equivalent. Thus at the beginning of chapter 15 “Of Paternal, Political and Despotic Power Considered Together” he writes:

THOUGH I have had occasion to speak of these before, yet the great mistakes of late about government, having as I suppose arisen from confounding these distinct powers one with another, it may not be amiss, to consider them together.

Chapters 6 and 7 give Locke’s account of paternal and political power respectively. Paternal power is limited. It lasts only through the minority of children, and has other limitations. Political power, derived as it is from the transfer of the power of individuals to enforce the law of nature, has with it the right to kill in the interest of preserving the rights of the citizens or otherwise supporting the public good. Legitimate despotic power, by contrast, implies the right to take the life, liberty, health and at least some of the property of any person subject to such a power.

At the end of the Second Treatise we learn about the nature of illegitimate civil governments and the conditions under which rebellion and regicide are legitimate and appropriate. As noted above, scholars now hold that the book was written during the Exclusion Crisis, and may have been written to justify a general insurrection and the assassination of the king of England and his brother. The argument for legitimate revolution follows from making the distinction between legitimate and illegitimate civil government. A legitimate civil government seeks to preserve its subjects’ life, health, liberty, and property insofar as this is compatible with the public good. Because it does this, it deserves obedience. An illegitimate civil government seeks to systematically violate the natural rights of its subjects. It seeks to make them illegitimate slaves. Because an illegitimate civil government does this, it puts itself in a state of nature and a state of war with its subjects. The magistrate or king of such a state violates the law of nature and so makes himself into a dangerous beast of prey who operates on the principle that might makes right, or that the strongest carries it. In such circumstances, rebellion is legitimate, as is the killing of such a dangerous beast of prey. Thus Locke justifies rebellion and regicide under certain circumstances. Presumably, this justification was going to be offered for the killing of the King of England and his brother had the Rye House Plot succeeded. Even if this was not Locke’s intention, it still would have served that purpose admirably.

The issue of religious toleration was of widespread interest in Europe in the seventeenth century, largely because religious intolerance with accompanying violence was so pervasive. The Reformation had split Europe into competing religious camps, and this provoked civil wars and massive religious persecutions. John Marshall, in his massive study John Locke, Toleration and Early Enlightenment Culture notes that the 1680s were the climactic decade for this kind of persecution. The Dutch Republic, where Locke spent years in exile, had been founded as a secular state which would allow religious differences. This was a reaction to the Catholic persecution of Protestants. However, once the Calvinist Church gained power, they began persecuting other sects, such as the Remonstrants, who disagreed with them. Nonetheless, The Dutch Republic remained the most tolerant country in Europe. In France, religious conflict had been temporarily quieted by the edict of Nantes. But in 1685, the year in which Locke wrote the First Letter concerning religious toleration, Louis XIV had revoked the Edict of Nantes, and the Huguenots were being persecuted. Though prohibited from doing so, some 200,000 emigrated, while probably 700,000 were forced to convert to Catholicism. People in England were keenly aware of the events taking place in France.

In England itself, religious conflict dominated the seventeenth century, contributing in important respects to the coming of the English Civil War, and the abolishing of the Anglican Church during the Protectorate. After the Restoration of Charles II, Anglicans in parliament passed laws that repressed both Catholics and Protestant sects such as Presbyterians, Baptists, Quakers and Unitarians who did not agree with the doctrines or practices of the state Church. Of these various dissenting sects, some were closer to the Anglicans, others more remote. One reason, among others, why King Charles may have found Shaftesbury useful was that they were both concerned about religious toleration. They parted when it became clear that the King was mainly interested in toleration for Catholics, and Shaftesbury for Protestant dissenters.

One widely discussed strategy for reducing religious conflict in England was called comprehension. The idea was to reduce the doctrines and practices of the Anglican church to a minimum so that most, if not all, of the dissenting sects would be included in the state church. For those which even this measure would not serve, there was to be toleration. Toleration we may define as a lack of state persecution. Neither of these strategies made much progress during the course of the Restoration.

When Locke fled to Holland after the discovery of the Rye house plot, he became involved with a group of scholars advocating religious toleration. This group included Benjamin Furly, a quaker with whom Locke lived for a while, the noted philosopher Pierre Bayle, several Dutch theologians, and many others. This group read all the arguments for religious intolerance and discussed them in book and conversation clubs. Members of the group considered toleration not only for Protestants and Protestant dissenters but Jews, Moslems, and Catholics. A recent discovery of a page of Locke’s reflections on toleration of Catholics shows that Locke considered even the pros and cons of toleration for Catholics (Walmsley and Waldmann 2019). Some members of the group also wrote tolerationist articles and books. They helped each other get jobs. Some of their members founded journals that reviewed books and articles on religious, scientific, and other topics. The group took the notion of free speech, civility, and politeness in discourse seriously. They called themselves the ‘the Republic of Letters’ or in Locke’s phrase ‘the commonwealth of learning.’

What were Locke’s religious views and where did he fit into the debates about religious toleration? This is a quite difficult question to answer. Religion and Christianity in particular, is perhaps the most important influence on the shape of Locke’s philosophy. But what kind of Christian was Locke? Locke’s family were Puritans. At Oxford, Locke avoided becoming an Anglican priest. Still, Locke himself claimed to be an Anglican until he died and Locke’s nineteenth-century biographer Fox Bourne thought that Locke was an Anglican. Others have identified him with the Latitudinarians—a movement among Anglicans to argue for a reasonable Christianity that dissenters ought to accept. Still, there are some reasons to think that Locke was neither an orthodox Anglican or a Latitudinarian. Locke got Isaac Newton to write Newton’s most powerful anti-Trinitarian tract. Locke arranged to have the work published anonymously in Holland though in the end, Newton decided not to publish (McLachlan 1941). This strongly suggests that Locke too was by this time an Arian or unitarian. (Arius, c. 250–336, asserted the primacy of the Father over the Son and thus rejected the doctrine of the Trinity and was condemned as a heretic at the Council of Nicaea in 325. Newton held that the Church had gone in the wrong direction in condemning Arius.) Given that one main theme of Locke’s Letter on Toleration is that there should be a separation between Church and State, this does not seem like the view of a man devoted to a state religion. It might appear that Locke’s writing The Reasonableness of Christianity in which he argues that the basic doctrines of Christianity are few and compatible with reason make him a Latitudinarian. Yet Richard Ashcraft has argued that comprehension for the Anglicans meant conforming to the existing practices of the Anglican Church; that is, the abandonment of religious dissent. Ashcraft also suggests that Latitudinarians were thus not a moderate middle ground between contending extremes but part of one of the extremes—“the acceptable face of the persecution of religious dissent” (Ashcraft 1992: 155). Ashcraft holds that while the Latitudinarians may have represented the “rational theology” of the Anglican church, there was a competing dissenting “rational theology”. Thus, while it is true that Locke had Latitudinarian friends, given Ashcraft’s distinction between Anglican and dissenting “rational theologies”, it is entirely possible that The Reasonableness of Christianity is a work of dissenting “rational theology”.

Locke had been thinking, talking and writing about religious toleration since 1659. His views evolved. In the early 1660s he very likely was an orthodox Anglican. He and Shaftesbury had instituted religious toleration in the Fundamental Constitutions of the Carolinas (1669). He wrote the Epistola de Tolerantia in Latin in 1685 while in exile in Holland. He very likely was seeing Protestant refugees pouring over the borders from France where Louis XIV had just revoked the Edict of Nantes. Holland itself was a Calvinist theocracy with significant problems with religious toleration. But Locke’s Letter does not confine itself to the issues of the time. Locke gives a principled account of religious toleration, though this is mixed in with arguments which apply only to Christians, and perhaps in some cases only to Protestants. He excluded both Catholics and atheists from religious toleration. In the case of Catholics it was because he regarded them as agents of a foreign power. Because they do not believe in God, atheists, on Locke’s account: “Promises, covenants and oaths, which are the bonds of human society, can have no hold upon an atheist” (Mendus 1991: 47). He gives his general defense of religious toleration while continuing the anti-Papist rhetoric of the Country party which sought to exclude James II from the throne.

Locke’s arguments for religious toleration connect nicely to his account of civil government. Locke defines life, liberty, health and property as our civil interests. These are the proper concern of a magistrate or civil government. The magistrate can use force and violence where this is necessary to preserve civil interests against attack. This is the central function of the state. One’s religious concerns with salvation, however, are not within the domain of civil interests, and so lie outside of the legitimate concern of the magistrate or the civil government. In effect, Locke adds an additional right to the natural rights of life, liberty, health and property—the right of freedom to choose one’s own road to salvation. (See the section on Toleration in the entry on Locke’s Political Philosophy.)

Locke holds that the use of force by the state to get people to hold certain beliefs or engage in certain ceremonies or practices is illegitimate. The chief means which the magistrate has at her disposal is force, but force is not an effective means for changing or maintaining belief. Suppose then, that the magistrate uses force so as to make people profess that they believe. Locke writes:

A sweet religion, indeed, that obliges men to dissemble, and tell lies to both God and man, for the salvation of their souls! If the magistrate thinks to save men thus, he seems to understand little of the way of salvation; and if he does it not in order to save them, why is he so solicitous of the articles of faith as to enact them by a law? (Mendus 1991: 41)

So, religious persecution by the state is inappropriate. Locke holds that “Whatever is lawful in the commonwealth cannot be prohibited by the magistrate in the church”. This means that the use of bread and wine, or even the sacrificing of a calf could not be prohibited by the magistrate.

If there are competing churches, one might ask which one should have the power? The answer is clearly that power should go to the true church and not to the heretical church. But Locke claims this amounts to saying nothing. For every church believes itself to be the true church, and there is no judge but God who can determine which of these claims is correct. Thus, skepticism about the possibility of religious knowledge is central to Locke’s argument for religious toleration.

Finally, for an account of the influence of Locke’s works, see the supplementary document: Supplement on the Influence of Locke’s Works

Locke’s Works

Oxford University Press is in the process of producing a new edition of all of Locke’s works. This will supersede The Works of John Locke of which the 1823 edition is probably the most standard. The new Clarendon editions began with Peter Nidditch’s edition of An Essay Concerning Human Understanding in 1975. The Oxford Clarendon editions contain much of the material of the Lovelace collection, purchased and donated to Oxford by Paul Mellon. This treasure trove of Locke’s works and letters, which includes early drafts of the Essay and much other material, comes down from Peter King, Locke’s nephew, who inherited Locke’s papers. Access to these papers has given scholars in the twentieth century a much better view of Locke’s philosophical development and provided a window into the details of his activities which is truly remarkable. Hence the new edition of Locke’s works will very likely be definitive.

• [N] An Essay Concerning Human Understanding , Peter H. Nidditch (ed.), 1975. doi:10.1093/actrade/9780198243861.book.1/actrade-9780198243861-book-1
• Some Thoughts Concerning Education , John W. Yolton and Jean S. Yolton (eds.), 1989. doi:10.1093/actrade/9780198245827.book.1/actrade-9780198245827-book-1
• Drafts for the Essay Concerning Human Understanding, and Other Philosophical Writings: In Three Volumes , Vol. 1: Drafts A and B, Peter H. Nidditch and G. A. J. Rogers (eds.), 1990. doi:10.1093/actrade/9780198245452.book.1/actrade-9780198245452-book-1
• The Reasonableness of Christianity: As Delivered in the Scriptures , John C. Higgins-Biddle (ed.), 2000. doi:10.1093/actrade/9780198245254.book.1/actrade-9780198245254-book-1
• An Essay Concerning Toleration: And Other Writings on Law and Politics, 1667–1683 , J. R. Milton and Philip Milton (eds.), 2006. doi:10.1093/actrade/9780199575732.book.1/actrade-9780199575732-book-1
• Vindications of the Reasonableness of Christianity , Victor Nuovo (ed.), 2012. doi:10.1093/actrade/9780199286553.book.1/actrade-9780199286553-book-1
• volume 1, 1987. doi:10.1093/actrade/9780198248019.book.1/actrade-9780198248019-book-1
• volume 2, 1987. doi:10.1093/actrade/9780198248064.book.1/actrade-9780198248064-book-1
• Volume 1, 1991. doi:10.1093/actrade/9780198245469.book.1/actrade-9780198245469-book-1
• Volume 2, 1991,. doi:10.1093/actrade/9780198248378.book.1/actrade-9780198248378-book-1
• Vol. 1: Introduction; Letters Nos. 1–461 , 2010. doi:10.1093/actrade/9780199573615.book.1/actrade-9780199573615-book-1
• Vol. 2: Letters Nos. 462–848 , 1976. doi:10.1093/actrade/9780198245599.book.1/actrade-9780198245599-book-1
• Vol. 3: Letters Nos. 849–1241 , 1978. doi:10.1093/actrade/9780198245605.book.1/actrade-9780198245605-book-1
• Vol. 4: Letters Nos. 1242–1701 , 1978. doi:10.1093/actrade/9780198245612.book.1/actrade-9780198245612-book-1.
• Vol. 5: Letters Nos. 1702–2198 , 1979. doi:10.1093/actrade/9780198245629.book.1/actrade-9780198245629-book-1
• Vol. 6: Letters Nos. 2199–2664 , 1980. doi:10.1093/actrade/9780198245636.book.1/actrade-9780198245636-book-1
• Vol. 7: Letters Nos. 2665–3286 , 1981. doi:10.1093/actrade/9780198245643.book.1/actrade-9780198245643-book-1
• Vol. 8: Letters Nos. 3287–3648 , 1989. doi:10.1093/actrade/9780198245650.book.1/actrade-9780198245650-book-1

In addition to the Oxford Press edition, there are a few editions of some of Locke’s works which are worth noting.

• An Early Draft of Locke’s Essay, Together with Excerpts from his Journal , Richard I. Aaron and Jocelyn Gibb (eds.), Oxford: Clarendon Press, 1936.
• John Locke, Two Tracts of Government , Phillip Abrams (ed.), Cambridge: Cambridge University Press, 1967.
• Locke’s The Two Treatises of Civil Government , Richard Ashcraft (ed.), London: Routledge, 1987.
• [Axtell 1968], The Educational Writings of John Locke: A Critical Edition , James L. Axtell (ed.), Cambridge: Cambridge University Press.
• [Gay 1964], John Locke on Education , Peter Gay (ed.), New York: Bureau of Publications, Columbia Teachers College, 1964.
• Epistola de Tolerantia: A Letter on Toleration , Latin text edited with a preface by Raymond Klibansky; English translation with an introduction and notes by J. W. Gough, Oxford: Oxford University Press, 1968.
• [G&T 1996] “Some Thoughts Concerning Education” and “The Conduct of the Understanding” , Ruth W. Grant and Nathan Tarcov (eds), Indianapolis: Hackett Publishing Co., 1996.
• [Laslett 1960] Locke’s Two Treatises of Government , Peter Laslett (ed.), Cambridge: Cambridge University Press, 1960.
• [Woozley 1964], An Essay Concerning Human Understanding , abridged, A.D. Woozley (ed.), London: Fontana Library, 1964.

Other Primary Sources

• Boyle, Robert, 1675 [1979], “Some Physico-Theological Considerations About the Possibility of the Resurrection”, in Selected Philosophical Papers of Robert Boyle , M.A. Stewart (ed.), New York: Manchester University Press.
• Mill, John Stuart, 1843, A System of Logic Ratiocinative and Inductive , London: John W. Parker.

Biographies

• King, Lord Peter, 1991, The Life of John Locke: with extracts from his correspondence, journals, and common-place books , Bristol: Thoemmes.
• Fox Bourne, H.R., 1876, Life of John Locke , 2 volumes, New York: Harper & Brothers. Reprinted Scientia Aalen, 1969.
• Cranston, Maurice, 1957, John Locke, A Biography , reprinted Oxford: Oxford University Press, 1985.
• Woolhouse, Roger, 2007, Locke: A Biography , Cambridge: Cambridge University Press.

Books and Articles

• Aaron, Richard, 1937, John Locke , Oxford: Oxford University Press.
• Aarsleff, Hans, 1982, From Locke to Saussure: Essays on the Study of Language and Intellectual History , Minneapolis: University of Minnesota Press.
• –––, 1994 “Locke’s Influence”, in Vere Chappell (ed.), The Cambridge Companion to Locke , Cambridge: Cambridge University Press, pp. 252–289. doi:10.1017/CCOL0521383714.011
• Alexander, Peter, 1985, Ideas Qualities and Corpuscles: Locke and Boyle on the External World , Cambridge: Cambridge University Press.
• Alston, William and Jonathan Bennett, 1988, “Locke on People and Substances”, The Philosophical Review , 97(1): 25–46. doi:10.2307/2185098
• Anstey, Peter R., 2011, John Locke and Natural Philosophy , Oxford: Oxford University Press. doi:10.1093/acprof:oso/9780199589777.001.0001
• Armitage, David, 2004, “John Locke, Carolina and the Two Treatises of Government ”, Political Theory , 32(5): 602–27. doi:10.1177/0090591704267122
• Arneil, Barbara, 1996, John Locke and America , Oxford: Clarendon Press.
• Ashcraft, Richard, 1986, Revolutionary Politics and Locke’s Two Treatises of Civil Government , Princeton: Princeton University Press.
• –––, 1992, “Latitudinarianism and Toleration: Historical Myth versus Political History”, in Kroll, Ashcraft, and Zagorin 1992: 151–177. doi:10.1017/CBO9780511896231.008
• Ayers, Michael, 1991, Locke: Epistemology and Ontology , 2 volumes, London: Routledge.
• Barresi, John, and Raymond Martin, 2000, Naturalization of the Soul: Self and Personal Identity in the 18th Century , London: Routledge.
• Bennett, Jonathan, 1971, Locke, Berkeley, Hume: Central Themes , Oxford: Oxford University Press.
• Bolton, Martha Brandt, 2004, “Locke on the Semantic and Epistemic Role of Simple Ideas of Sensation”, Pacific Philosophical Quarterly , 85(3): 301–321. doi:10.1111/j.1468-0114.2004.00200.x
• Brandt, Reinhard (ed.), 1981, John Locke: Symposium Wolfenbuttel 1979 , Berlin: de Gruyter.
• Brewer, Holly, 2017, “Slavery, Sovereignty, and ‘Inheritable Blood’: Reconsidering John Locke and the Origins of American Slavery”, The American Historical Review , 122(4): 1038–1078. doi:10.1093/ahr/122.4.1038
• Chappell, Vere, 1992, Essays on Early Modern Philosophy, John Locke—Theory of Knowledge , London: Garland Publishing, Inc.
• –––, 1994, The Cambridge Companion to Locke , Cambridge: Cambridge University Press.
• –––, 2004a, “Symposium: Locke and the Veil of Perception: Preface”, Pacific Philosophical Quarterly , 85(3): 243–244. doi:10.1111/j.1468-0114.2004.00196.x
• –––, 2004b, “Comments”, Pacific Philosophical Quarterly , 85(3): 338–355. doi:10.1111/j.1468-0114.2004.00202.x
• Chomsky, Noam, 1966, Cartesian Linguistics: A Chapter in the History of Rationalist Thought , New York: Harper & Row.
• Dunn, John, 1969, The Political Thought of John Locke , Cambridge: Cambridge University Press.
• Farr, James, 2008, “Locke, Natural Law and New World Slavery”, Political Theory , 36(4): 495–522. doi:10.1177/0090591708317899
• Fox, Christopher, 1988, Locke and the Scriblerians , Berkeley: University of California Press.
• Garrett, Don, 2003, “Locke on Personal Identity, Consciousness and ‘Fatal Errors’”, Philosophical Topics , 31: 95–125. doi:10.5840/philtopics2003311/214
• Geach, Peter, 1967, “Identity”, The Review of Metaphysics , 21(1): 3–12.
• Gibson, James, 1968, Locke’s Theory of Knowledge and its Historical Relations , Cambridge: Cambridge University Press.
• Gordon-Roth, Jessica, 2015, “Locke’s Place-Time-Kind Principle”, Philosophy Compass , 10(4): 264–274. doi:10.1111/phc3.12217
• Grant, Ruth, 1987, John Locke’s Liberalism , Chicago: University of Chicago Press.
• Gaukroger, Stephen, 2010, The Collapse of Mechanism and the Rise of Sensibility: Science and the Shaping of Modernity 1680–1760 , Oxford, Clarendon Press.
• Kretzmann, Norman, 1968, “The Main Thesis of Locke’s Semantic Theory”, The Philosophical Review , 77(2): 175–196. Reprinted in Tipton 1977: 123–140. doi:10.2307/2183319
• Kroll, Peter, Richard Ashcraft, and Peter Zagorin (eds), 1992, Philosophy, Science and Religion in England 1640–1700 , Cambridge: Cambridge University Press. doi:10.1017/CBO9780511896231
• Jolley, Nicholas, 1984, Leibniz and Locke , Oxford: Oxford University Press.
• –––, 1999, Locke, His Philosophical Thought , Oxford: Oxford University Press.
• –––, 2015, Locke’s Touchy Subjects: Materialism and Immortality , Oxford: Oxford University Press. doi:10.1093/acprof:oso/9780198737094.001.0001
• Laslett, Peter, 1954 [1990], “John Locke as Founder of the Board of Trade”, The Listener , 52(1342): 856–857. Reprinted in J.S. Yolton 1990: 127–136.
• Lennon, Thomas M., 2004, “Through a Glass Darkly: More on Locke’s Logic of Ideas”, Pacific Philosophical Quarterly , 85(3): 322–337. doi:10.1111/j.1468-0114.2004.00203.x
• LoLordo, Antonia, 2010, “Person, Substance, Mode and ‘the moral Man’ in Locke’s Philosophy”, Canadian Journal Of Philosophy , 40(4); 643–668. doi:10.1080/00455091.2010.10716738
• Lott, Tommy, 1998, Subjugation and Bondage: Critical Essays on Slavery and Social Philosophy , New York: Rowman and Littlefield Publishers Inc.
• Lovejoy, Arthur O., 1936, The Great Chain of Being; a Study of the History of an Idea , Cambridge, MA: Harvard University Press.
• Lowe, E.J., 1995, Locke on Human Understanding , London: Routledge Publishing Co.
• Mackie, J. L. 1976, Problems from Locke , Oxford: Clarendon Press.
• Macpherson, C.B., 1962, The Political Theory of Possessive Individualism , Oxford: Oxford University Press.
• Mandelbaum, Maurice, 1966, Philosophy, Science and Sense Perception: Historical and Critical Studies , Baltimore: The John Hopkins University Press.
• Marshall, John, 2006, John Locke, Toleration and Early Enlightenment Culture , Cambridge UK, Cambridge University Press.
• Martin, C. B. and D. M. Armstrong (eds.), 1968, Locke and Berkeley: A Collection of Critical Essays , New York: Anchor Books.
• Mattern, Ruth, 1980, “Moral Science and the Concept of Persons in Locke”, The Philosophical Review , 89(1): 24–45. doi:10.2307/2184862
• McCann, Edwin, 1987, “Locke on Identity, Life, Matter and Consciousness” Archiv für Geschichte der Philosophie , 69(1): 54–77. doi:10.1515/agph.1987.69.1.54
• McLachlan, Hugh, 1941, Religious Opinions of Milton, Locke and Newton , Manchester: Manchester University Press.
• Mendus, Susan, 1991, Locke on Toleration in Focus , London: Routledge.
• Newman, Lex, 2004, “Locke on Sensitive Knowledge and the Veil of Perception—Four Misconceptions”, Pacific Philosophical Quarterly , 85(3): 273–300. doi:10.1111/j.1468-0114.2004.00199.x
• Olsthoorn, Johan and Laurens van Apeldoorn, 2020, “‘This man is my property’: Slavery and political absolutism in Locke and the classical social contract tradition”, European Journal of Political Theory , 21(2): 253–275. doi:10.1177/1474885120911309
• Rogers, G.A. John, 2004, “Locke and the Objects of Perception”, Pacific Philosophical Quarterly , 85(3): 245–254. doi:10.1111/j.1468-0114.2004.00197.x
• Roper, John, April 2004, Conceiving Carolina: Proprietors, Planters and Plots 1662–1729 , New York, Palgrave/Macmillan.
• Russell, Daniel, 2004, “Locke on Land and Labor”, Philosophical Studies , 117(1–2): 303–325. doi:10.1023/B:PHIL.0000014529.01097.20
• Schouls, Peter, 1992, Reasoned Freedom: John Locke and the Enlightenment , Ithaca, NY: Cornell University Press.
• Simmons, A. John, 1992, The Lockean Theory of Rights , Princeton: Princeton University Press.
• Soles, David, 1999, “Is Locke an Imagist?” The Locke Newsletter , 30: 17–66.
• Strawson, Galen, 2011, Locke on Personal Identity , Princeton: Princeton University Press.
• Stuart, Matthew, 2013, Locke’s Metaphysics , Oxford: Oxford University Press. doi:10.1093/acprof:oso/9780199645114.001.0001
• Thiel, Udo, 2011, The Early Modern Subject: Self-Consciousness and Personal Identity from Descartes to Hume , Oxford: Oxford University Press. doi:10.1093/acprof:oso/9780199542499.001.0001
• Tarcov, Nathan, 1984, Locke’s Education for Liberty , Chicago: The University of Chicago Press.
• Tipton, I.C. (ed.), 1977, Locke on Human Understanding: Selected Essays , Oxford: Oxford University Press.
• Tully, James, 1980, A Discourse on Property , Cambridge: Cambridge University Press.
• –––, 1993, An Approach to Political Philosophy: Locke in Contexts , Cambridge: Cambridge University Press.
• Uzgalis, William L., 1988, “The Anti-Essential Locke and Natural Kinds”, The Philosophical Quarterly , 38(152): 330–339. doi:10.2307/2220132
• –––, 1990, “Relative Identity and Locke’s Principle of Individuation”, History of Philosophy Quarterly , 7(3): 283–297.
• –––, 2007, Locke’s Essay Concerning Human Understanding—A Reader’s Guide , London: Continuum.
• –––, 2017, “John Locke, Racism, Slavery and Indian Lands”, in Naomi Zack (ed.), The Oxford Handbook to Philosophy and Race , Oxford: Oxford University Press.
• Walmsley, Jonathan and Waldman Felix, 2019 “John Locke and Toleration of Catholics: A New Manuscript”, Historical Journal , 62: 1093–1115. [Includes transcription of “Reasons for tolerating papists with others” St. Johns College, Annapolis, Maryland, Greenfield Library.]
• Wilson, Margaret Dauler, 1999, Ideas and Mechanism: Essays on Early Modern Philosophy , Princeton: Princeton University Press.
• Wilson, Thomas D., 2016, The Ashley Cooper Plan: The Founding of Carolina and the Origins of Southern Political Culture , Chapel Hill, NC: University of North Carolina Press.
• Wood, Neal, 1983, The Politics of Locke’s Philosophy , Berkeley: University of California Press.
• Woolhouse, R.S., 1971, Locke’s Philosophy of Science and Knowledge , New York: Barnes and Noble.
• –––, 1983, Locke , Minneapolis: University of Minnesota Press.
• –––, 1988, The Empiricists , Oxford: Oxford University Press.
• Yaffe, Gideon, 2000, Liberty Worth the Name: Locke on Free Agency , Princeton: Princeton University Press.
• –––, 2004, “Locke on Ideas of Substance and the Veil of Perception”, Pacific Philosophical Quarterly , 85(3): 252–272. doi:10.1111/j.1468-0114.2004.00198.x
• Yolton, Jean S., 1990, A Locke Miscellany , Bristol: Thoemmes Antiquarian Books.
• Yolton, John, 1956, John Locke and the Way of Ideas Oxford, Oxford University Press; reprinted, Bristol: Thoemmes Press, 1996.
• –––, 1969, John Locke: Problems and Perspectives: New Essays , Cambridge: Cambridge University Press.
• –––, 1970, John Locke and the Compass of Human Understanding , Cambridge: Cambridge University Press.
• –––, 1983, Thinking Matter: Materialism in Eighteenth Century Britain , Minneapolis: University of Minnesota Press.
• –––, 1984, Perceptual Acquaintance: From Descartes to Reid , Minneapolis: University of Minnesota Press.

Bibliographies

• Hall, Roland, and Roger Woolhouse, 1983, 80 Years of Locke Scholarship: A Bibliographical Guide , Edinburgh: University of Edinburgh Press.
• Locke Studies (formerly The Locke Newsletter) , edited by Timothy Stanton, Heslington: University of York.

How to cite this entry . Preview the PDF version of this entry at the Friends of the SEP Society . Look up topics and thinkers related to this entry at the Internet Philosophy Ontology Project (InPhO). Enhanced bibliography for this entry at PhilPapers , with links to its database.

• “John Locke” , entry on Locke, Internet Encyclopedia of Philosophy .
• Images of Locke , National Portrait Gallery, Great Britain.

Berkeley, George | Hume, David | Leibniz, Gottfried Wilhelm | liberalism | Locke, John: moral philosophy | Locke, John: on freedom | Locke, John: on personal identity | Locke, John: philosophy of science | Locke, John: political philosophy | Masham, Lady Damaris | personal identity | substance | tropes

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• Introduction

Theory of ideas

Primary and secondary qualities, personal identity, association of ideas.

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An Essay Concerning Human Understanding

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• Table Of Contents

An Essay Concerning Human Understanding ,

work by the English philosopher John Locke , published in 1689, that presents an elaborate and sophisticated empiricist account of the nature, origins, and extent of human knowledge. The influence of An Essay Concerning Human Understanding was enormous, perhaps as great as that of any other philosophical work apart from those of  Plato  (428/427–348/347 bce ) and  Aristotle (348–322 bce ). Its importance in the English-speaking world of the 18th century can scarcely be overstated. Along with the works of René Descartes , it constitutes the foundation of modern  Western philosophy .

A dominant theme of the Essay is the question: What is the capacity of the human mind for understanding and knowledge? In his prefatory chapter, Locke explains that the Essay is not offered as a contribution to knowledge itself but as a means of clearing away some of the intellectual rubbish that stands in the way of knowledge. He had in mind not only the medieval Scholastics and their followers but also some of his older contemporaries. The Scholastics—those who took Aristotle and his commentators to be the source of all philosophical knowledge and who still dominated teaching in universities throughout Europe—were guilty of introducing technical terms into philosophy (such as substantial form , vegetative soul , abhorrence of a vacuum , and intentional species ) that upon examination had no clear sense or, more often, no sense at all. Locke saw the Scholastics as an enemy that had to be defeated before his own account of knowledge could be widely accepted—a judgment in which he was entirely right.

Locke begins the Essay by repudiating the view that certain kinds of knowledge—knowledge of the existence of God , of certain moral truths, or of the laws of logic or mathematics —are innate, or imprinted on the human mind at its creation. (The doctrine of innate ideas , which was widely held to justify religious and moral claims, had its origins in the philosophy of Plato, who was still a powerful force in 17th-century English philosophy.) Locke argues to the contrary that an idea cannot be said to be “in the mind” until one is conscious of it. But human infants have no conception of God or of moral, logical, or mathematical truths, and to suppose that they do, despite obvious evidence to the contrary, is merely an unwarranted assumption to save a position. Furthermore, travelers to distant lands have reported encounters with people who have no conception of God and who think it morally justified to eat their enemies. Such diversity of religious and moral opinion cannot be explained by the doctrine of innate ideas but can be explained, Locke held, on his own account of the origins of ideas.

In Book II he turns to that positive account. He begins by claiming that the sources of all knowledge are, first, sense experience (the red colour of a rose, the ringing sound of a bell, the taste of salt, and so on) and, second, “reflection” (one’s awareness that one is thinking, that one is happy or sad, that one is having a certain sensation, and so on). These are not themselves, however, instances of knowledge in the strict sense, but they provide the mind with the materials of knowledge. Locke calls the materials so provided “ideas.” Ideas are objects “before the mind,” not in the sense that they are physical objects but in the sense that they represent physical objects to consciousness .

All ideas are either simple or complex. All simple ideas are derived from sense experience, and all complex ideas are derived from the combination (“compounding”) of simple and complex ideas by the mind. Whereas complex ideas can be analyzed, or broken down, into the simple or complex ideas of which they are composed, simple ideas cannot be. The complex idea of a snowball, for example, can be analyzed into the simple ideas of whiteness, roundness, and solidity (among possibly others), but none of the latter ideas can be analyzed into anything simpler. In Locke’s view, therefore, a major function of philosophical inquiry is the analysis of the meanings of terms through the identification of the ideas that give rise to them. The project of analyzing supposedly complex ideas (or concepts) subsequently became an important theme in philosophy, especially within the analytic tradition, which began at the turn of the 20th century and became dominant at Cambridge , Oxford , and many other universities, especially in the English-speaking world.

In the course of his account, Locke raises a host of related issues, many of which have since been the source of much debate. One of them is his illuminating distinction between the “primary” and “secondary” qualities of physical objects. Primary qualities include size, shape, weight, and solidity, among others, and secondary qualities include colour, taste, and smell. Ideas of primary qualities resemble the qualities as they are in the object—as one’s idea of the roundness of a snowball resembles the roundness of the snowball itself. However, ideas of secondary qualities do not resemble any property in the object; they are instead a product of the power that the object has to cause certain kinds of ideas in the mind of the perceiver. Thus, the whiteness of the snowball is merely an idea produced in the mind by the interaction between light, the primary qualities of the snowball, and the perceiver’s sense organs.

Locke discussed another problem that had not before received sustained attention: that of personal identity . Assuming one is the same person as the person who existed last week or the person who was born many years ago, what fact makes this so? Locke was careful to distinguish the notion of sameness of person from the related notions of sameness of body and sameness of human being . Sameness of body requires identity of matter, and sameness of human being depends on continuity of life (as would the sameness of a certain oak tree from acorn to sapling to maturity), but sameness of person requires something else. Locke’s proposal was that personal identity consists of continuity of consciousness . One is the same person as the person who existed last week or many years ago if one has memories of the earlier person’s conscious experiences. Locke’s account of personal identity became a standard (and highly contested) position in subsequent discussions.

A further influential section of Book II is Locke’s treatment of the association of ideas. Ideas, Locke observes, can become linked in the mind in such a way that having one idea immediately leads one to form another idea, even though the two ideas are not necessarily connected with each other. Instead, they are linked through their having been experienced together on numerous occasions in the past. The psychological tendency to associate ideas through experience, Locke says, has important implications for the education of children. In order to learn to adopt good habits and to avoid bad ones, children must be made to associate rewards with good behaviour and punishments with bad behaviour. Investigations into the associations that people make between ideas can reveal much about how human beings think. Through his influence on researchers such as the English physician David Hartley (1705–57), Locke contributed significantly to the development of the theory of associationism, or associationist psychology, in the 18th century. Association has remained a central topic of inquiry in psychology ever since.

Having shown to his satisfaction that no idea requires for its explanation the hypothesis of innate ideas, Locke proceeds in Book III to examine the role of language in human mental life. His discussion is the first sustained philosophical inquiry in modern times into the notion of linguistic meaning. As elsewhere, he begins with rather simple and obvious claims but quickly proceeds to complex and contentious ones. Words, Locke says, stand for ideas in the mind of the person who uses them. It is by the use of words that people convey their necessarily private thoughts to each other. In addition, Locke insists, nothing exists except particulars, or individual things. There are, for example, many triangular things and many red things, but there is no general quality or property, over and above these things, that may be called “triangle” (“triangularity”) or “red” (“redness”) ( see universal ). Nevertheless, a large number of words are general in their application, applying to many particular things at once. Thus, words must be labels for both ideas of particular things (particular ideas) and ideas of general things (general ideas). The problem is, if everything that exists is a particular, where do general ideas come from?

Locke’s answer is that ideas become general through the process of abstraction. The general idea of a triangle, for example, is the result of abstracting from the properties of specific triangles only the residue of qualities that all triangles have in common—that is, having three straight sides. Although there are enormous problems with this account, alternatives to it are also fraught with difficulties.

In Book IV of the Essay , Locke reaches the putative heart of his inquiry, the nature and extent of human knowledge. His precise definition of knowledge entails that very few things actually count as such for him. In general, he excludes knowledge claims in which there is no evident connection or exclusion between the ideas of which the claim is composed. Thus, it is possible to know that white is not black whenever one has the ideas of white and black together (as when one looks at a printed page), and it is possible to know that the three angles of a triangle equal two right angles if one knows the relevant Euclidean proof. But it is not possible to know that the next stone one drops will fall downward or that the next glass of water one drinks will quench one’s thirst, even though psychologically one has every expectation, through the association of ideas, that it will. These are cases only of probability, not knowledge—as indeed is virtually the whole of scientific knowledge, excluding mathematics. Not that such probable claims are unimportant: humans would be incapable of dealing with the world except on the assumption that such claims are true. But for Locke they fall short of genuine knowledge.

There are, however, some very important things that can be known. For example, Locke agreed with Descartes that one can know immediately and without appeal to any further evidence that one exists at the time that one considers it. One can also know immediately that the colour of the print on a page is different from the colour of the page itself—i.e., that black is not white—and that two is greater than one. It can also be proved from self-evident truths by valid argument (by an argument whose conclusion cannot be false if its premises are true) that a first cause , or God, must exist. Various moral claims also can be demonstrated—e.g., that parents have a duty to care for their children and that one should honour one’s contracts. People often make mistakes or poor judgments in their dealings with the world or each other because they are unclear about the concepts they use or because they fail to analyze the relevant ideas. Another great cause of confusion, however, is the human propensity to succumb to what Locke calls “Enthusiasm,” the adoption on logically inadequate grounds of claims that one is already disposed to accept.

One major problem that the Essay appears to raise is that, if ideas are indeed the immediate objects of experience, how is it possible to know that there is anything beyond them—e.g., ordinary physical objects? Locke’s answer to this problem, insofar as he recognized it as a problem, appears to have been that, because perception is a natural process and thus ordained by God, it cannot be generally misleading about the ontology of the universe. In the more skeptical age of the 18th century, this argument became less and less convincing. This issue dominated epistemology in the 18th century.

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Essay Concerning Human Understanding

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Introduction

Love it or hate it, no contemporary student of philosophy can ignore John Locke's Essay Concerning Human Understanding . Initially published in December of 1689, it has been one of the most influential books of the last three centuries; in fact, it is not much of a stretch to say that every subsequent philosopher has been touched by Locke's ideas in some way. The unique importance of Locke's Essay lies in the fact that it is the first systematic presentation of an *empiricist* philosophy of mind and cognition: a theory of knowledge and belief based wholly on the principle that everything in our mind gets there by way of experience. The first principle of an empiricist philosophy of mind is often illustrated by the notion of a Tabula Rasa, or a blank slate (an illustration Locke himself made famous in the Essay ): at birth, our minds arrive into this world completely empty, like a pure white sheet of paper, and it is only as experience "writes" on this paper that ideas and thoughts begin to form.

As the first explicit formulation of an empiricist philosophy, the Essay had a profound effect upon the intellectual climate of the late 17th century, which until then was wholly dominated by two warring camps, the established Aristotelian *Scholastics* on the one hand and the upstart Cartesian *rationalists* on the other. Locke, with his thoroughgoing, but rational, empiricism, cut a middle road through these two extreme positions, and offered an alternative view of the world and our access to it, which proved enticing to many thinkers. Roughly contemporary empiricists such as George Berkeley, and slightly later ones such David Hume, built their philosophies on the foundation Locke had laid out. Kant, seeking to reconcile empiricism with rationalism in the late 18th century, drew heavily from Locke's work, in large part giving precise and novel formulation to ideas which stemmed originally from the Essay . Even in the 20th century, empiricists such as Rudolph Carnap, G.E. Moore, and W.V. Quine, explicitly expressed their debt to Locke's writings. Locke's contribution to empiricism can hardly be overstated; not only did he give us one of the most detailed and plausible accounts of the position to date, but, in a sense, he spurred the entire movement with his innovative ideas.

The Essay , though, is far from a narrow work on a single topic. It is, in fact, staggeringly wide-ranging, covering such diverse topics as philosophy of language, philosophy of logic, moral philosophy, and philosophy of religion in addition to the better known philosophy of mind and cognition. Locke treats each of these topics intelligibly and provocatively, making his book a convenient starting point for students and scholars alike.

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An Essay Concerning Human Understanding

by John Locke

Last Updated on October 26, 2018, by eNotes Editorial. Word Count: 1282

John Locke’s purpose in An Essay Concerning Human Understanding is to inquire into the origin and extent of human knowledge. His conclusion—that all knowledge is derived from sense experience—became the principal tenet of empiricism, which has dominated Western philosophy ever since. Even George Berkeley, who rejected Locke’s distinction between sense qualities independent of the mind and sense qualities dependent on the mind, produced his idealism in response to Locke’s provocative philosophy and gave it an empirical cast that reflected Western culture’s rejection of innate or transcendental knowledge.

An Essay Concerning Human Understanding is divided into four books: book 1, “Of Innate Notions”; book 2, “Of Ideas”; book 3, “Of Words”; and book 4, “Of Knowledge, Certain and Probable.”

In preparation for his radical claim that all ideas are derived from experience, Locke begins his essay with a careful consideration of the thesis that there are innate ideas. Locke first examines the notion that there are ideas that are a necessary part of human understanding and are, therefore, common to all people. Locke’s attack on this thesis is from two directions. He argues that many of the ideas that are supposed to be innate can be and have been derived naturally from sense experience, that not all people assent to those ideas that are supposed to be innate. Locke maintains that even if reason enables people to discover the truth of certain ideas, those ideas cannot be said to be innate, for reason is needed to discover their truth.

In book 2, “Of Ideas,” Locke considers the origin of such ideas as those expressed by the words “whiteness,” “hardness,” “sweetness,” “thinking,” “motion,” “man,” and the like. The second section states his conclusion: Let us then suppose the mind to be, as we say, white paper void of all characters, without any ideas. How comes it to be furnished? . . . Whence has it all the materials of reason and knowledge? To this I answer, in one word, from experience. . . . Our observation, employed either about external sensible objects, or about the internal operations of our minds perceived and reflected on by ourselves, is that which supplies our understandings with all the materials of knowledge.

The two sources of ideas, according to Locke, are sensation and reflection. By the senses people come to have perceptions of things, thereby acquiring the ideas of yellow, white, or cold, for example. Then, by reflection, by consideration of the mind in operation, people acquire the ideas of thinking, doubting, believing, knowing, willing, and so on.

By sensation people acquire knowledge of external objects; by reflection people acquire knowledge of their own minds. Ideas that are derived from sensation are simple; that is, they present “one uniform appearance,” even though a number of simple ideas may come together in the perception of an external object. The mind dwells on the simple ideas, comparing them to one another, combining them, but never inventing them. By a “simple idea” Locke means what some modern and contemporary philosophers have called a “sense-datum,” a distinctive, entirely differentiated item of sense experience, such as the odor of some particular glue or the taste of coffee in a cup. He calls attention to the fact that people use sense experience to imagine what they have never perceived, but no operation of the mind can yield novel simple ideas.

By the quality of something, Locke means its power to produce an idea in someone sensing the thing. The word “quality” is used in the essay in much the same way the word “characteristic” or “property” has been used by other writers. Locke distinguishes between primary and secondary qualities. Primary qualities are those that matter has constantly, whatever its state. As primary qualities Locke names solidity, extension, figure, motion or rest, and number. By secondary qualities Locke means the power to produce various sensations that have nothing in common with the primary qualities of the external objects. Thus, the power to produce the taste experience of sweetness is a secondary quality of sugar, but there is no reason to suppose that the sugar itself possesses the distinctive quality of the sensation. Colors, tastes, sounds, and odors are secondary qualities of objects. Locke also refers to a third kind of quality or power, called simply “power,” by which he means the capacity to affect or to be affected by other objects. Thus, fire can melt clay; the capacity to melt clay is one of fire’s powers, and such a power is neither a primary nor a secondary quality.

Locke concludes that primary ideas resemble external objects, but secondary ideas do not. It is this particular claim that excited other professional philosophers, with Berkeley arguing that primary qualities can be understood only in terms of human sensations, so that whatever generalization can be made about secondary qualities would have to cover primary qualities as well, and with other philosophers arguing that Locke had no ground for maintaining that primary ideas “resemble” primary qualities, even if the distinction between primary and secondary qualities is allowed.

Complex ideas result from acts of the mind, and they fall into three classes: ideas of modes, of substances, and of relations. Modes are ideas that are considered to be incapable of independent existence since they are affections of substance, such as the ideas of triangle, gratitude, and murder. To think of substances is to think of “particular things subsisting by themselves,” and to think in that manner involves supposing that there is a support, which cannot be understood, and that there are various qualities in combination which give various substances their distinguishing traits. Ideas of relations are the result of comparing ideas with each other.

After a consideration of the complex ideas of space, duration, number, the infinite, pleasure and pain, substance, relation, cause and effect, and of the distinctions between clear and obscure ideas and between true and false ideas, Locke proceeds to a discussion, in book 3, of words and essences. Words are signs of ideas by “arbitrary imposition,” depending upon observed similarities that are taken as the basis for considering things in classes. Words are related to “nominal essences,” that is, to obvious similarities found through observation, and not to “real essences,” the actual qualities of things. Locke then discusses the imperfections and abuses of words.

In book 4, Locke defines knowledge as “the perception of the connection of and agreement, or disagreement and repugnancy, of any of our ideas.” An example cited is one’s knowledge that white is not black, Locke arguing that to know that white is not black is simply to perceive that the idea of white is not the idea of black.

Locke insists that knowledge cannot extend beyond the ideas one has, and that people determine whether ideas agree or disagree with each other either directly, by intuition, or indirectly, by reason or sensation. Truth is defined as “the joining or separating of signs, as the things signified by them do agree or disagree one with another.” For example, the proposition “White is not black” involves the separation by “is not” of the signs “white” and “black,” signifying the disagreement between the ideas of white and black; since the ideas are different, the proposition is true. Actually to have compared the ideas and to have noted their disagreement is to know the fact that the true proposition signifies.

Locke devotes the remaining chapters of book 4 to arguing that people have knowledge of their existence by intuition, of the existence of God by demonstration, and of other things by sensation. Here the influence of René Descartes is clearly evident. It is the empiricism of the earlier parts of the book that won for Locke the admiration of philosophers.

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• An Essay Concerning Human Understanding Summary

by John Locke

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Written by people who wish to remain anonymous

Locke's An Essay Concerning Human Understanding is an epistemology, or a study of the phenomenon of human knowledge and belief.

In Book I, he turns to the question of nature vs nurture, and he argues against the idea that a human is born with a set of innate ideas or beliefs. Rather, he argues that humans are born without ideas or thoughts, but that through experience, they construct their worldview one moment at a time.

In Book II, Locke outlines a division between passive and active learning, stating that beliefs that come into the mind from passive methods tend to be more simply, whereas complex ideas, especially abstract ideas like numbers and math, are acquired with active participation, with effort. He also outlines another division, a division between qualities, saying that primary qualities can be known as truly extant, where as secondary qualities are more like what the object represents to the subjective experience of the person. In other words, an apple is a red object, but to a human, it's food.

In Book III, Locke turns to the question of language and the way language shapes the mind. Locke describes the way words signify ideas, and he makes the claim that man is unique in his linguistic abilities. (Trying to specify what the essential difference between mankind and the animal kingdom was very popular during this season of philosophy).

In Book IV, the final chapter of the essay, the subject of the essay broadens to discuss the nature of knowledge, offering a true ontology along with his epistemology. By saying a thing can be known, Locke argues that they have made an ontological assumption, but it's not clear that humans have the objectivity to make those kinds of truth claims, so ultimately, human intuition is assumption. He ends the work outlining the various categories for the sciences.

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An Essay Concerning Human Understanding study guide contains a biography of John Locke, literature essays, quiz questions, major themes, and a full summary and analysis.

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An Essay Concerning Human Understanding essays are academic essays for citation. These papers were written primarily by students and provide critical analysis of An Essay Concerning Human Understanding by John Locke.

• Locke’s Proof Against Innate Mathematical Knowledge
• Locke, Blake, and Wordsworth: Understanding Experience
• On the Nature of Ideas and Human Understanding: Comparing Locke and Berkeley

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• > Leibniz: New Essays on Human Understanding
• > Introduction

Book contents

• Frontmatter
• Acknowledgements
• Introduction
• Abbreviations
• Further reading
• Notes on the translation
• Note on the edition
• New Essays on Human Understanding
• Book I Of innate notions
• Book II Of ideas
• Book III Of words
• Book IV Of knowledge
• Index of names
• Index of topics
• List of examples
• More titles in the Cambridge texts in the history of philosophy series

Published online by Cambridge University Press:  05 June 2012

The history of the Nouveaux essais

Within five years of the first appearance of Locke's Essay Concerning Human Understanding (1690), Leibniz had read at least some of it, and had written several pages of comments – some appreciative, some mildly critical – upon parts of the work, allowing an intermediary to pass them on to Locke. The latter received them sourly, writing to a friend with a sceptical allusion to Leibniz's ‘great name’, and concluding that ‘even great parts will not master any subject without great thinking, and even the largest minds have but narrow swallows’ (Locke to Molyneux, April 1697). The letter containing that remark was published in 1708, and Leibniz later wrote: ‘I am not surprised by it: we differed rather too much in principles’ (Leibniz to Rémond, March 1714).

Leibniz's interest in Locke's work is abundantly shown by his correspondence in the 1690s, by his re-working the comments mentioned above, and by his writing a fresh set of remarks on Books 1 and 11 of the Essay , as well as (in 1698) a longer commentary on the controversy which the Essay had stirred up between Locke and Stillingfleet, the Bishop of Worcester.

The English language must have been something of a barrier between Leibniz and Locke's long, difficult book. In a letter admitting the imperfections in his French, he wrote: ‘I only wish I had the same knowledge of the English language; but not having had the occasion for it, the most I can manage is a tolerable understanding of books written in that language’; and on p. 462 of the present work there is a small but striking indication of his not being at home with English.

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• G. W. Leibniz
• Edited by Peter Remnant , Jonathan Bennett
• Book: Leibniz: New Essays on Human Understanding
• Online publication: 05 June 2012
• Chapter DOI: https://doi.org/10.1017/CBO9781139166874.001

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