An Essay Concerning Human Understanding

views updated

An Essay Concerning Human Understanding

by John Locke


An essay in four books written in Holland and England in the late 1600s; published in London in 1690.


A philosophical inquiry into the origins, nature, and limits of human knowledge, the essay refutes the belief that humans are born with some ideas (such as God) already formed in their minds. It proposes that all ideas are formed by experience, that the mind uses words to stand for ideas, and that all knowledge results from the interplay of ideas.

Events in History at the Time of the Essay

The Essay in Focus

For More Information

Commonly acknowledged to be the most influential philosopher writing in English, John Locke (1632-1704) was a thinker whose career spanned a wide range of fields. His skills included those of educator, scientist, physician, diplomat, economist, theologian, civil servant, and political theorist. Locke played each of these roles at various times in his professional life. He spent one year as a lecturer at Oxford University, where he had been an undergraduate in the 1650s. In 1666 Locke accepted a position as personal physician to Anthony Ashley Cooper, later the earl of Shaftesbury. The two men became friends, and as Shaftesbury became embroiled in a political struggle with King Charles II during the 1670s, he came to rely on Locke for political as well as medical advice. In 1675, for reasons of health, Locke moved to France, where he read the highly influential philosophical works of René Descartes (1596-1650). He returned to England in 1679, just as Shaftesbury’s conflict with the king was coming to a head. With Shaftesbury’s political defeat in 1681 and flight to Holland the following year, Locke’s own position in England became insecure, and he too fled to Holland in 1683. Locke had begun writing An Essay Concerning Human Understanding in 1671, and in Holland he resumed the project in earnest. Returning to England in 1688, he finished the book, published it in 1690, and continued to refine it in accord with the dynamic intellectual exchanges of his time.

Events in History at the Time of the Essay

Cartesian rationalism

In the first half of the seventeenth century, the French philosopher René Descartes revolutionized European thought with the apparently simple declaration: Cogito ergo sum (“I think, therefore I am”). The notion underlying this statement is that all things are subject to doubt—except for the act of doubting, or reasoning, itself, and thus the mind that reasons or doubts. Reason, for Descartes, is the faculty of mind capable of establishing certain knowledge (a point that Locke’s essay would dispute). On this foundation, Descartes, and the Jewish Spaniard from Amsterdam, Baruch Spinoza (1632-77), as well as others, built the intellectual structure of seventeenth-century rationalism, which ultimately posited that reason was not only the basis of existence but also the source of all knowledge. Any truth, the rationalists maintained, could be arrived at by the independent exercise of reason alone, without external verification—that is, without referring to the outside world as it is perceived by the senses.

Also crucial to the rationalists’ argument was Descartes’s doctrine of innate ideas, which held (in keeping with the independence of reason) that certain important ideas exist in the human mind from birth and therefore are fully formed before any perceptions of the outside world might bring them into being. Indeed, in some rationalist writings these innate ideas are the starting points from which reason articulates any given truth. The doctrine of innate ideas was widely accepted by the time Locke began work on An Essay, and he devotes Book I (of the four books that comprise the work) to refuting it.

Francis Bacon and induction

While the rationalists (most of whom lived on the European continent) developed their view of how humans know and understand things, a few English thinkers were moving in a very different, and in some ways opposite, direction. This English tradition is commonly held to have originated in the thought of Sir Francis Bacon (1561-1626), the essayist, lawyer, scientist, philosopher, and statesman who played important roles in the administrations of Elizabeth I (ruled 1558-1603) and her successor, James I (ruled 1603-1625). In contrast to the rationalists’ use of innate ideas as a starting point for knowledge, Bacon proposed instead that the freely inquiring mind is, in the famous Latin phrase, a tabula rasa—a “blank slate”—on which such knowledge as the world itself supplies is impartially recorded. In other words, knowledge is properly acquired precisely without preexisting ideas, by a process Bacon called “induction”: the accumulation of perceived sensory data to the point at which the perceiver can then extract general principles, or underlying truths, that give shape or meaning to this data.

Bacon’s technique of induction would help give rise to the philosophical position known as “empiricism.” In contrast to rationalism, empiricism holds that all knowledge derives from the senses, through their perception of the outside world. Locke and other English philosophers and scientists of the seventeenth century regarded Bacon as their intellectual father; Locke’s Essay has been regarded by some as the definitive statement of the empiricist position.

The new experimental science

The philosophical debate in the seventeenth century over the origins and nature of knowledge took place in the context of the scientific revolution that had begun in the sixteenth century. Starting with the work of astronomers Nicholas Copernicus (1473-1543), Johannes Kepler (1571-1630), and Galileo Galilei (1564-1642), scientists had brought new techniques into play that changed forever humanity’s view of the universe and our place in it. This new scientific approach was based on both observation (for example, Galileo’s use of the telescope) and reason (for example, Copernicus’s conclusion that the planets revolve around the sun). Taking the new approach a step further, Galileo brought observation and reason together in the crucial innovation of a scientific method—the experiment.

While Francis Bacon had not been a very accomplished scientist himself (in particular, he ignored the potential of mathematics in describing nature), he did bring some valuable and refreshing new approaches to the practice of science. Aware of Galileo’s work in Italy, Bacon took up the new experimental method and integrated it into his larger theory, which included the logic of induction. It was in his advocacy of experiments, not in his espousal of induction, that Bacon’s contributions were most valuable to later generations of scientists.

Indeed, induction threatened to hobble the experimental method, for part of Bacon’s inductive method was to reject the predictive hypothesis as an explanatory tool. Hypotheses, Bacon believed, could only cloud the gathering of pure data by introducing preconceptions into the mind of the scientist. (Bacon’s reasoning ignores the inescapable fact that an experiment must have some hypothesis, even if it is unstated, otherwise the experiment would be aimless.) In his rejection of hypotheses, Bacon was reacting against the pure rationalism of medieval Scholasticism, which had relied on speculative hypotheses unchecked by sensory data and therefore ungrounded in physical reality. Bacon’s radical rejection of this outmoded tradition was so attractive to his followers that generations of English scientists believed, falsely, that they were practicing pure induction. “Hypotheses non fingo”(“I frame no hypotheses”), claimed the most brilliant of them, the Englishman whom the opening pages of Locke’s Essay calls “the incomparable Mr Newton” (Newton, p. 371; Locke, Essay Concerning Human Understanding, p. 11).

Isaac Newton and the Royal Society

In the genius of Isaac Newton (1642-1727), the scientific revolution begun by Copernicus found its culmination. A mathematical genius as well as a formidable experimentalist, Newton combined the strongest elements of the rationalist and empiricist traditions. Newton’s laws of motion put the physics experiments of Galileo on sound theoretical footing, and his related law of gravity did the same for the astronomical ideas of Copernicus and Kepler. To express his theories mathematically, Newton invented a new mathematical language, the calculus (which was independently invented in mainland Europe by the rationalist G. W. von Leibniz). Newton published his findings in the Philosophiae Naturalis Principia Math-ematica(Mathematical Principles of Natural Philosophy, commonly called the Principia) in 1687, as Locke was completing the Essay.

Locke and Newton both belonged to the first scientific association in England (and one of the first in Europe), the Royal Society of London for the Promotion of Natural Knowledge. The Royal Society, now a conservative bastion of the scientific community, was at the cutting edge of the new experimental method when it was founded in 1660. Locke was elected to the Royal Society in 1668, and Newton in 1671. Among the society’s founding members were the father of modern chemistry, Robert Boyle; the microscopist, physicist, and inventor Robert Hooke; and the architect Christopher Wren. Locke also engaged in intellectual exchanges with scientists outside the Royal Society, such as physician Thomas Syden-ham (1624-89), a founder of modern clinical


The opposing viewpoints of rationalism and empiricism both originate in the writings of the Greek philosophers of the fifth and fourth centuries b.c.e. Plato stressed what he called “ideas,” universal truths that exist in perfect form apart from, and beyond the reach of, the senses. In Phaedo, Plato suggested that concepts such as equality, for example, cannot be apprehended by the senses and must therefore exist in the soul before the birth of the body. Plato proposed his theories in reaction to the fifth-century b.c.e. Greek philosophers known as the Sophists, who had discounted the power of reason in favor of practical observation. Plato’s student Aristotle, while exalting the role of reason, also championed observation and experience, comparing the mind to a blank slate in his work On the Soul.

medicine, and Dutch astronomer, physicist, and mathematician Christian Huygens (1629-95).

These and other scientists were carrying on a complex program of experiment and observation, which gave rise to an energetic debate about scientific methods. Boyle and Hooke, for example, championed the usefulness of carefully tested hypotheses; Hooke, in fact, engaged in a bitter dispute with Newton partly over Newton’s claim not to have framed any hypotheses. Locke himself accepted the validity of framing a hypothesis, while at the same time endorsing a Baconian reliance on observation: “He, that would not deceive himself, ought to build his hypothesis on matter of fact, and make it out by sensible [sensory] experience” (Essay, p. 113).

The problem was partly one of language: what exactly was meant by words like hypothesis? In the seventeenth century, scientific terms had not yet been carefully defined and were consequently used in many different, even contradictory, ways. Today, scientists distinguish between hypothesis,an unconfirmed explanatory proposition; theory, a set of propositions that entails certain observational consequences and is to some degree confirmed; and scientific law, a general proposition that is highly confirmed. (Newton’s mathematical description of gravitation is accepted as a law.) While these are modern definitions, Locke too addresses such linguistic issues, devoting Book III of the Essay to language and meaning, which he recognizes as basic to the process of understanding.

Politics, religion, and science

Locke was ten years old when the English Civil War (1642-49) broke out; he came of age during the war and the following eleven-year period in which Oliver Cromwell and Parliament ruled England as a “commonwealth,” having deposed and executed King Charles I in 1649. Called the Interregnum, this period ended with the restoration of King Charles II in 1660. Cromwell and his strongest supporters in Parliament were Puritans, and many of the scientific attitudes of the age can be thought of as springing from the same profound questioning of received authority that led the Puritans to dispute the status quo in government (like the divine right of kings) and in religion (like the necessity of ecclesiastic hierarchy). Locke’s own religious views are generally characterized as Puritan. A willingness to question authority is central not only to his philosophical thought but to his highly influential political thought, as well.

After Charles II took the throne, the opposition to strong royal power was manifested in the formation of the Whig party, which opposed the Tories, or the party of the king. The Whigs engineered the removal of Charles II’s brother and successor, the Catholic King James II, in 1688; this so-called Glorious or Bloodless Revolution installed the Dutch Protestant Prince William of Orange and his wife Mary (James’s Protestant daughter) as joint rulers of England. Locke’s friend and employer Shaftesbury was a leader of the Whigs and, on account of his writings, Locke himself is often viewed as the formulator of Whig political theory. Shaftesbury died in Holland in 1683, and Locke returned from Holland with Mary after the Whig victory in 1688. It was in this political environment that he was able to finish and publish the Essay and his other major works.

The Essay in Focus

Contents summary

The four parts of the Essay are titled as follows: “Book I, Of Innate Notions”; “Book II, Of Ideas”; “Book III, Of Words”; “Book IV, Of Knowledge and Opinion.” Book I begins with a brief introduction that states Locke’s purpose: “to inquire into the original, certainty, and extent of human knowledge; together with the grounds and degrees of belief, opinion and assent” (Essay, p. 55). The book will examine, in turn, three main subjects: first, the origins of the ideas that come into our minds and of which we are conscious; second, the knowledge that we think we gain from those ideas, how certain that knowledge is, what evidence it is based on, and how far it extends; and, finally, faith and opinion, by which Locke means our assent to propositions of whose truth we have no certain knowledge.

Locke then proceeds to his arguments against the existence of “innate principles” or “notions” (Essay, p. 59). First, Locke asserts that “children and idiots” do not possess the ideas that are claimed to be innate, for example simple propositions such as “Whatever is, is” (Essay, p. 60). This is enough to prove that such ideas cannot be inborn, for if they were, children would have them. If not innate, he asks, how do ideas come into our minds? There is only one way possible: gradually and through the senses. “The senses at first let in particular ideas, and furnish the yet empty cabinet: and the mind by degrees growing familiar with some of them, they are lodged in the memory” (Essay, p. 65). A child can tell sweet from bitter long before it knows the difference between the general concepts of sweetness and bitterness; it learns the concepts from the sensory experience of tasting sweet and bitter things repeatedly over time. The mistake made by those who endorse innate ideas is to assume that simply because certain concepts (such as sweetness or bitterness) seem universal, those concepts must be inborn; what the supporters of innate ideas do not realize is that common experience could also supply them.

In Book II (“Of Ideas”) Locke begins by tackling the question of how that process works. In a famous passage, he supposes the mind to be like

white paper, void of all characters, without any ideas; how comes it to be furnished? Whence comes it by that vast store, which the busy and boundless fancy of man has painted on it, with an almost endless variety? Whence has it all the materials of reason and knowledge? To this I answer in one word, from experience: in that, all our knowledge is founded, and from that it ultimately derives itself.

(Essay, p. 109)

There are two ways in which experience provides the ideas that furnish our minds: some ideas (sweetness, for example) come into it directly from sensation; other ideas arise from the mind’s own operation (doubting or believing, for example) and come into it through what Locke calls “reflection” (Essay, p. 109). Both kinds of ideas, which Locke groups together as “simple ideas,” vary from person to person, depending on what sorts of things people come into contact with (sensation) in their environments and how their own minds operate (reflection) (Essay, p. 121). What Locke calls “complex ideas” (for example, horse, gold, beauty, or the universe) are formed by combining simple ideas in various ways (Essay, p. 159). What distinguishes a complex idea is that it can be broken down into its component ideas, yet it still exists as a nameable bundle of ideas in its own right. All our ideas, even the most complicated, arise from such combinations of simple ideas, which, in turn, are derived from either sensation or reflection.


Locke’s political ideas were published in his Two Treatises of Government(1690), in which he asserts that legitimate government is based on a social contract between persons in nature, whereby each agrees to transfer his or her executive power to a central government and so becomes a citizen of a civil society. The contract relies on the consent of the governed. It follows that if the ruler fails to promote justice, the subjects have the right, even the duty, to revolt. Aside from formulating the Whigs’ liberal political agenda for the century to come, Locke’s political thought provided the theoretical basis for the American Revolution. Also articulated in the treatises were concepts such as the separation of powers (through checks and balances between branches of government) that inspired the framers of the United States Constitution.

Locke goes on to consider worldly objects that produce sensations (which in turn create ideas in the mind). Material objects can possess two kinds of qualities, he says, which he calls primary and secondary: primary qualities are those that are inherent in an object itself, such as its size, shape, texture, or the movement of its parts; secondary qualities are those that vary according to how they are perceived, such as sound, taste, smell, or color. Perception itself is a mental phenomenon, Locke continues, so that secondary qualities depend on the mind of the perceiver as well as on his senses. For the remainder of Book II, Locke considers the various ways that the qualities of objects—their perception by the senses and the mind, and the ideas that result—can combine to form other more sophisticated ideas. He discusses some of the basic and more sophisticated ideas in detail (philosophers still find much of his analysis relevant today). Major examples include thinking, pleasure, pain, power, cause and effect, identity, madness, truth, and falseness. The simple ideas of pleasure and pain, for example, can combine in different ways to form more complex ideas—passions such as love, hatred, desire, or joy.

At the beginning of Book III (“Of Words”), Locke declares that God has given humans the capacity for making articulate sounds, which allows people to take an idea that they experience and give it a name—that is, to use a word for it. Human words, then, are “names which stand for ideas” (Essay, p. 361). It is through the use of these names that people communicate their ideas to each other, rather than through the ideas themselves, which remain “invisible, hidden from others, nor can of themselves be made to appear” (Essay, p. 363). Yet these invisible ideas are still fundamentally traceable to sensory experience, and Locke suggests that all words, including those for abstract concepts, have their origins in the concrete:

Spirit, in its primary signification, is breath; angel, a messenger: and I doubt not, but if we could trace them to their sources, we should find, in all languages, the names, which stand for things that fall not under our senses, to have had their first rise from sensible ideas.

(Essay, p. 362)

In contrast to the medieval Scholastic theory that words represent the “real essences” of what they signify, Locke proposes that words represent general ideas constructed by us, which are “nominal essences.” Gold, for example, does not represent a real essence, but a nominal, agreed-upon essence based on defining attributes, such as yellow, malleable, fusible, and soluble. It is a general word for a complex idea, a category people who use the word have agreed on for convenience (Essay, p. 374). Definition, Locke goes on, “is nothing else, but showing the meaning of one word by several other not synonymous terms” (Essay, p. 378). But, he adds, words for “simple ideas, and those only, are incapable of being defined,” since simple ideas are those that cannot be broken down into other ideas, separate components, which would be necessary in order to create a definition (Essay, p. 378). Language is not perfect, Locke cautions, and “the very nature of words, makes it almost unavoidable, for many of them to be doubtful and uncertain in their significations” (Essay, p. 424). Taking advantage of such ambiguities, people often abuse language, using words inconsistently or distorting their meanings so that their audiences are misled. Such abuse can be either deliberate or negligent.

Having laid the groundwork that he believes necessary for a discussion of knowledge, in Book IV (“Of Knowledge and Opinion”) Locke arrives at the essay’s climax. “Knowledge,” he states at the outset, is nothing but “the perception of the connexion and agreement, or disagreement and repugnancy of any of our ideas. In this alone it consists” (Essay, p. 467). The agreement or disagreement between ideas can be “intuitive”—that is, when we perceive it without recourse to intermediate ideas—or “demonstrative”—that is, when we perceive it only through the mediation of other ideas (Essay, p. 471). A third and less sophisticated kind of knowledge, which Locke calls “sensitive knowledge,” comes directly from our experience of “particular external objects” (Essay, p. 477-78). Outside of these three kinds of knowledge, anything else we think we know merely amounts to “faith” or “opinion” (Essay, p. 477). Furthermore, because our ideas themselves are beset by doubts and uncertainties, “the extent of our knowledge comes not only short of the reality of things, but even of the extent of our own ideas” (Essay, p. 479). Thus, in most cases, certain knowledge is illusory, though probable knowledge (a conclusion whose likelihood is sufficient to compel assent) may be commonly attained.

Locke stipulates two areas of knowledge that are exceptions to this prevailing uncertainty: mathematics and morality, in both of which he asserts that knowledge is certain. This is because both moral and mathematical ideas are “archetypes” of themselves, a term Locke uses but does not define (Essay, p. 501). Indeed, he further claims, any time an idea is the archetype of itself—or conforms exactly to that archetype—then and only then is certainty possible. Knowledge, which comes from ideas, thus depends for its accuracy on the accuracy of those ideas. Similarly, truth as well “is about ideas agreeing to things” (Essay, p. 511). From these assertions Locke argues that individuals should not accept what others tell them to be true or certain without attempting independently to verify such statements themselves. Yet within these limitations people can and often must act as if something were true, even if it cannot be strictly verified. We may thus offer limited assent to any proposition that is consistent with our own observations and “comes attested to by the reports of all who mention it” (Essay, p. 584).

Locke defines “reason” as “the discovery of the certainty or probability of such propositions or truths, which the mind arrives at … by sensation or reflection”; “faith,” by contrast, is “the assent to any proposition, not thus made out by the deductions of reason; but upon the credit of the proposer, as coming from God, in some extraordinary way of communication” (Essay, p. 608). Faith is less certain than reason, he says, and propositions on faith should not be accepted where they run contrary to reason. It is easy for a believer to be led astray, so special care should be given in assenting to matters of faith. “Belief,” Locke cautions, “is no proof of revelation” (Essay, p. 621).

Still, Locke allows, fewer people assent to erroneous opinions than is commonly imagined. He puts all of human knowledge within three categories:

First, the nature of things, as they are in themselves, their relations, and their manner of operation: or secondly, that which man himself ought to do [how he ought to behave], for the attainment of any end, especially happiness: or thirdly, the ways and means, whereby the knowledge of both the one and the other of these, are attained and communicated.

(Essay, p. 634)

The first he calls “natural philosophy.” the second “ethics,” and the last “the doctrine of signs” (Essay, pp. 634-35). These three areas, he concludes, make up “the three great provinces of the intellectual world, wholly separate and distinct one from another” (Essay, p. 635).

Rationalism, empiricism, and probability

While Locke has sometimes been called the father of empiricism, his approach to epistemology, or the study of thought, also contains elements that clearly come from the European rationalist tradition. Locke’s identification of mathematics as an area of certain knowledge, for example, confirms the validity of this central feature of rationalist doctrine. Yet mathematics itself was expanding from a medium perceived as transmitting certainty to one capable as well of expressing probability. Scholars have identified this shift as “helping to shape a mathematics more suited to scientific inquiry”; a major feature of the new experimental science was a movement away from casting conclusions as certain fact to presenting them as more or less probable depending on circumstances (Shapiro, p. 38). The emphasis on probability rather than certainty remains essential to the practice of science today.

Locke devotes an important chapter in Book IV to probability, which he calls “the appearance of agreement upon fallible proofs” (Essay, p. 577). Agreement between ideas, it will be recalled, constitutes knowledge in Locke’s scheme; probability, then, is the appearance of such agreement on less than clinching evidence. Infallible proof, as Locke has striven to demonstrate, is, in practice, hard to come by:

Most of the propositions we think, reason, discourse, nay act upon, are such, as we cannot have undoubted knowledge of their truth: yet some of them border so near upon certainty, that we make no doubt at all about them; but assent to them as firmly, and act, according to that assent, as resolutely, as if they were infallibly demonstrated, and that our knowledge of them was certain and perfect.

(Essay, p. 578)

The rest of Book IV, Locke continues, will be dedicated to exploring in detail the “degrees” of such probability, “from the very neighborhood of certainty … even to the confines of impossibility” (Essay, p. 578).

Scientists today tend to accept the world as a slippery place, in which absolute statements are to be regarded with suspicion and in which theories about how nature works must be treated as provisional rather than final. This realization lies at the core of the scientific revolution that reached its climax in Locke’s lifetime. Neither Descartes’s rigid rationalism nor Bacon’s rigid reliance on sense could be made to fit the new science, whose practitioners were forced to recognize that both reason and the senses could easily be deceived by the natural world’s immense complexities. Locke’s achievement lies in his attempt to map the gray areas that emerged, as acquiring knowledge became less a matter of resting on absolutes—on pure reason alone, or pure experience, or pure certainty, or pure speculation—and more a matter of disciplined selection from a varied yet structured palette of choices once regarded as absolutes.

Sources and literary context

Locke was not the first to recognize the illusory nature of certainty and the importance of probability. In this he followed the French scientist, philosopher, and mathematician Pierre Gassendi (1592-1655), who also stressed the probable nature of knowledge. Gassendi’s approach combined elements of rationalism and empiricism. He rejected Descartes’s innate ideas, emphasizing the senses and induction as primary sources of knowledge; yet he followed Descartes in relying on mathematics and accepting deduction, that is, drawing a conclusion by reasoning from given premises rather than by direct observation. Locke read both an edition of Descartes’s Meditations(1642) that contained an appendix of Gassendi’s criticisms and Gassendi’s own Disquisitio Metaphysica(Metaphysical Disquisition; 1644). His thinking was deeply influenced by these works, which, for example, suggested that ideas that enter the mind


There is a direct correspondence between ideas in Locke’s An Essay Concerning Human Understanding and literature produced a few decades later. One Lockean notion invoked by these writers is that animals, like humans, can reason, albeit on a lower level. Jonathan Swift in Gulliver’s Travels (1726; also in WLAIT 3: British and Irish Literature and Its Times) carries this notion to extremes, depicting animals that are more worthy of admiration than humans. At one point, Locke’s essay speaks of a blind man who says he understands the meaning of scarlet, whereupon a friend asks him to define it. Scarlet, explains the blind man, is like the sound of the trumpet; thus, he approximates what the color means—all that can be done, teaches the essay, when relying on words. Henry Fielding invokes this same blind man in Tom Jones (1749; also in WLAIT 3: British and Irish Literature and Its Times):“To treat of the effects of love to you must be as absurd as to discourse on colours to a man born blind” (Fielding in MacLean, p. 107). Finally, Laurence Sterne applied Locke’s teachings in Tristram Shandy(1759-67), whose narrator, for example, doubts what, if anything, he can know for certain and links the passage of time to the train or succession of ideas in one’s mind. It took a few decades, then, for Locke’s teachings to manifest themselves in fictional literary works, but the impact was ultimately very widespread. Especially from 1725 to 1765, England seemed to embrace Locke’s ideas about human understanding, despite the sometimes difficult-to-grasp logic and style that some readers associated with Locke’s writing.

through the senses can combine to form other ideas that might appear to have arisen purely from reason.

Of course, Descartes also directly influenced Locke. Though not mentioning the French philosopher by name, Locke tacitly recognizes the importance of Descartes’s ideas over and over, whether by rebutting them, adopting them outright, or adapting them to his own thought. He spends Book I rejecting Cartesian innate ideas, while his distinction among intuitive, demonstrative, and sensitive knowledge is taken directly from Descartes, and his concerns with the “original,” “certainty,” and “extent” of human knowledge, as well as with “ideas,” reflect central Cartesian concepts to which Locke takes his own approach.

Locke did not work in a vacuum; his thought represents a synthesis of ideas that were very much in the air during an age of intense intellectual activity. His Essay’s four books are prefaced by an introductory “Epistle to the Reader,” in which Locke sets out his reasons for embarking on the project. He relates how, in discussing a subject (he does not specify what it was), he and several friends found themselves rapidly mired in doubts and uncertainties:

After we had a while puzzled ourselves … it came into my thoughts … that, before we set ourselves on 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.

(Essay, p. 8)

Locke jotted down a few notes for the next meeting with his friends; these became the first drafts of the Essay, the rest of which was later “written by incoherent parcels; and, after long intervals of neglect, resumed again” (Essay, p. 8). Using imagery (the “commonwealth”) borrowed from the Interregnum, Locke also refers to the scientific revolution in which his friends and contemporaries were engaged:

The commonwealth of learning, is not at this time without its master-builders, whose mighty designs, in advancing the sciences, will leave lasting monuments to the admiration of posterity … in an age that produces such masters, as the great Huygenius [the Dutch physicist who discovered Saturn’s rings and was among the first to use pendulums in clocks], and the incomparable Mr Newton …’tis ambition enough to be employed as an under-laborer in clearing ground a little, and removing some of the rubbish that lies in the way to knowledge.

(Essay, p. 11)

Much of this “rubbish,” he continues, has been left by the pedantic and often “frivolous” use of abstruse scientific terms, which make science “unfit” for “polite conversation” (Essay, p. 11). Such scholarly jargon masks ignorance, hinders knowledge, and promotes vagueness. With his Essay, Locke hoped to “break in upon the sanctuary of vanity and ignorance” by explaining the nature of knowledge and understanding in plain, everyday language (Essay, p. 11).

Reception and impact

The first edition of the Essay was actually published in December 1689, though (following common publishers’ practice) it was dated 1690. It was followed by four other editions, in which Locke responded to criticisms and added new material, until the fifth edition of 1706, published two years after his death. Despite its length and difficulty, the Essay made an immediate impact on the English and European intellectual scene, and soon other works of philosophy began citing it heavily. In 1692, for example, in the preface to his own book, Dioptrica Nova, William Molyneux, a doctor from Dublin, Ireland, echoed Locke’s own praise of Newton in the following assessment of Locke’s contribution to logic:

To none do we owe for a greater advancement in this part of philosophy than to the incomparable Mr. Locke; who, in his Essay Concerning Human Understanding, has rectified more received mistakes, and delivered more profound truths … than are to be met in all the volumes of the Ancients.

(Molyneux in Cranston, John Locke, p. 359)

Locke wrote thanking Molyneux, and the two struck up a friendship that lasted until Molyneux’s death; in fact, Molyneux’s criticisms and suggestions were among those to which Locke responded in later editions of the Essay.

Not everyone was so complimentary, though. There was a general rivalry going on at the time between poets and philosophers. On the one hand, poets showed little patience for the seemingly trivial investigations of philosophers; on the other hand, philosophers showed little tolerance for the “romantic exaggerations” of the poets. John Dryden, leading poet of Locke’s age, disparaged philosophers; so to a degree did novelist Jonathan Swift, as shown in his Gulliver’s Travels (also in WLAIT 3: British and Irish Literature and Its Times). The minds of the scientists and philosophers in Laputa, points out Gulliver’s Travels, “are so taken up with intense speculations, that they neither can speak nor attend to the discourses of others, without being roused by some external taction upon the organs of speech and hearing” (Swift in MacLean, p. 9).

The church too took issue with philosophical notions of the time. The most strident negative criticisms came from Edward Stillingfleet, the Bishop of Worcester, who accused Locke of denying the dogma of the Trinity, prompting a lengthy debate in print, which is sometimes included as an appendix to the Essay. So upset were the pundits at Oxford University that they invoked measures in 1703 to prevent students from reading the essay. Within a few decades, though, resistance would diminish and champions of the essay would come to the fore; notable among them was Joseph Addison, the guiding hand behind the influential daily journal The Spectator (also in WLAIT 3:British and Irish Literature and Its Times). The Spectator began in 1711 to reproduce what it perceived as the finest ideas of its age, among them those contained in the excerpts that it published of Locke’s essay.

The impact of the Essay can be readily traced in such European movements as the Enlightenment, as well as in the tradition of British empiricism. This school of philosophical thought was taken up by George Berkeley (1685-1753) and continued into the twentieth century (in the work of Bertrand Russell and others). English literature too was deeply affected by Locke’s writings, beginning in the eighteenth century and continuing in later works, such as the 1811 Jane Austen novel Sense and Sensibility (also in WLAIT 3:British and Irish Literature and Its Times).

—Colin Wells

For More Information

Chappell, Vere, ed. The Cambridge Companion to Locke. Cambridge: Cambridge University Press, 1994.

Cranston, Maurice. John Locke. London: Longmans, 1966.

______. Introduction to Locke’s Essay Concerning Human Understanding, by John Locke. New York: Collier, 1965.

Gibson, James. Locke’s Theory of Knowledge and its Historical Relations. Cambridge: Cambridge University Press, 1968.

Jones, R. F. Ancients and Moderns. St. Louis: Washington University Studies, 1961.

Locke, John. An Essay Concerning Human Understanding. 1706. Reprint, London: Penguin Books, 1997.

MacLean, Russell. John Locke and English Literature of the Eighteenth Century. New York: Russell [and] Russell, 1962.

McCann, Edwin William. Locke’s Theory of Essence. Ann Arbor, Mich.: Xerox University Microfilms, 1975.

Newton, Isaac. Mathematical Principles of Natural Philosophy and His System of the World. Trans. Florian Cajori and Andrew Mott. Berkeley: University of California Press, 1934.

Shapiro, Barbara J. Probability and Certainty in Seventeenth Century England: A Study of the Relationships Between Natural Science, Religion, History, Law and Literature. Princeton: Princeton University Press, 1983.

Yolton, John. Locke and the Way of Ideas. Oxford: Oxford University Press, 1954.

Zook, Melinda S. Radical Whigs and Conspiratorial Politics in Late Stuart England. University Park, Penn.: Pennsylvania State University Press, 1999.

About this article

An Essay Concerning Human Understanding

Updated About content Print Article