John Locke, b. Aug. 29, 1632, d. Oct. 28, 1704, was an English philosopher and political theorist, the founder of British empiricism. He undertook his university studies at Christ Church, Oxford. At first, he followed the traditional classical curriculum but then turned to the study of medicine and science. Although Locke did not actually earn a medical degree, he obtained a medical license. He joined the household of Anthony Ashley Cooper, later 1st earl of Shaftesbury, as a personal physician. He became Shaftesbury's advisor and friend. Through him, Locke held minor government posts and became involved in the turbulent politics of the period.

In 1675, Locke left England to live in France, where he became familiar with the doctrines of René Descartes and his critics. He returned to England in 1679 while Shaftesbury was in power and pressing to secure the exclusion of James, duke of York (the future King James II) from the succession to the throne. Shaftesbury was later tried for treason, and although he was acquitted, he fled to Holland. Because he was closely allied with Shaftesbury, Locke also fled to Holland in 1683; he lived there until the overthrow (1688) of James II. In 1689, Locke returned to England in the party escorting the princess of Orange, who was to be crowned Queen Mary II of England. In 1691, Locke retired to Oates in Essex, the household of Sir Francis and Lady Masham. During his years at Oates, Locke wrote and edited, and received many influential visitors, including Sir Isaac Newton. He continued to exercise political influence. His friendships with prominent government officers and scholars made him one of the most influential men of the 17th century.

Locke's Essay Concerning Human Understanding (1690) is one of the classical documents of British empirical philosophy. The essay had its origin in a series of discussions with friends that led Locke to the conclusion that the principal subject of philosophy had to be the extent of the mind's ability to know. He set out "to examine our abilities and to see what objects our understandings were or were not fitted to deal with." The Essay is a principal statement of empiricism and, broadly speaking, was an effort to formulate a view of knowledge consistent with the findings of Newtonian science.

Locke began the Essay with a critique of the rationalistic idea that the mind is equipped with innate ideas, ideas that do not arise from experience. He then turned to the elaboration of his own empiricism: "Let us suppose the mind to be, as we say, white paper, void of all characters, without any ideas; how comes this to be furnished? . . . whence has it all the materials of reason and knowledge? To this I answer, in a word, from experience." What experience provides is ideas, which Locke defined as "the object of the understanding when a man thinks." He held that ideas come from two sources: sensation, which provides ideas about the external world, and reflection, or introspection, which provides the ideas of the internal workings of the mind.

Locke's view that experience produces ideas, which are the immediate objects of thought, led him to adopt a causal or representative view of human knowledge. In perception, according to this view, people are not directly aware of physical objects. Rather, they are directly aware of the ideas that objects "cause" in them and that "represent" the objects in their consciousness. A similar view of perception was presented by earlier thinkers such as Galileo and Descartes.

Locke's view raised the question of the extent to which ideas are like the objects that cause them. His answer was that only some qualities of objects are like ideas. He held that primary qualities of objects, or the mathematically determinable qualities of an object, such as shape, motion, weight, and number, exist in the world, and that ideas copy them. Secondary qualities, those which arise from the senses, do not exist in objects as they exist in ideas. According to Locke, secondary qualities, such as taste, "are nothing in the objects themselves but powers to produce ideas in use by their primary qualities." Thus, when an object is perceived, a person's ideas of its shape and weight represent qualities to be found in the object itself. Color and taste, however, are not copies of anything in the object.

One conclusion of Locke's theory is that genuine knowledge cannot be found in natural science, because the real essences of physical objects studied by science cannot be known. It would appear that genuine certainty can be achieved only through mathematics. Locke's view of knowledge anticipated developments by later philosophers and exercised an important influence on the subsequent course of philosophical thought.

Locke's considerable importance in political thought is better known. As the first systematic theorist of the philosophy of liberalism, Locke exercised enormous influence in both England and America. In his Two Treatises of Government (1690), Locke set forth the view that the state exists to preserve the natural rights of its citizens. When governments fail in that task, citizens have the right — and sometimes the duty — to withdraw their support and even to rebel. Locke opposed Thomas Hobbes's view that the original state of nature was "nasty, brutish, and short," and that individuals through a social contract surrendered — for the sake of self-preservation — their rights to a supreme sovereign who was the source of all morality and law. Locke maintained that the state of nature was a happy and tolerant one, that the social contract preserved the preexistent natural rights of the individual to life, liberty, and property, and that the enjoyment of private rights — the pursuit of happiness — led, in civil society, to the common good. Locke's notion of government was a limited one: the checks and balances among branches of government (later reflected in the U.S. Constitution) and true representation in the legislature would maintain limited government and individual liberties.

A Letter Concerning Toleration (1689) expressed Locke's view that, within certain limits, no one should dictate the form of another's religion. Other important works include The Reasonableness of Christianity (1695), in which Locke expressed his ideas on religion, and Some Thoughts Concerning Education (1693).

Thomas K. Hearn, Jr.

Bibliography: Aaron, R. I., John Locke, 3d ed. (1971); Ashcraft, Richard, ed., John Locke: Critical Assessments, 4 vols. (1991); Ayers, Michael, Locke (1993); Colman, John, John Locke's Moral Philosophy (1983); Chappell, Vere, ed., The Cambridge Companion to Locke (1994); Cranston, Maurice, John Locke: A Biography (1957; repr. 1985); Dunn, John, Political Thought of John Locke (1969; repr. 1983); Grant, R. W., John Locke's Liberalism (1987); Harris, Ian, The Mind of John Locke (1994); Marshall, John, John Locke (1994); Mabbott, J. D., John Locke (1973); Rogers, G. A. J., ed., Locke's Philosophy (1994); Sahakian, Mabel L. and William S., John Locke (1975); Tully, James, An Approach to Political Philosophy: Locke in Contexts (1993); Vaughn, Karen L., John Locke (1982); Yolton, J. W., John Locke and the Way of Ideas (1956) and, as ed., John Locke (1969).