John Locke (1632 - 1704)
English philosopher. His Essay concerning Human Understanding (1690) maintained that experience is the only source of knowledge (empiricism), and that 'we can have knowledge no farther than we have ideas' prompted by such experience. Two Treatises on Government (1690) helped to form contemporary ideas of liberal democracy.
Locke was born in Somerset and studied at Oxford. He practised medicine, and in 1667 became secretary to the Earl of Shaftesbury. He consequently fell under suspicion as a Whig and in 1683 fled to Holland, where he lived until the 1688 revolution brought William of Orange to the English throne. In later life he published many works on philosophy, politics, theology, and economics; these include Letters on Toleration (168992) and Some Thoughts concerning Education (1693).
For Locke, the physical universe was a mechanical system of material bodies, composed of corpuscules, or 'invisible particles'. He believed that at birth the mind was a blank, and that all ideas came from sense impressions.
In 1675, Locke left England to live in France, where he became familiar with the doctrines of Rene 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.
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. Colour 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 that science studies 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.
In political theory he was equally influential. Contradicting Hobbes, Locke maintained that the original state of nature was happy and characterized by reason and tolerance; all human beings were equal and free to pursue life, health, liberty, and possessions. The state formed by the Social Contract was guided by the natural law, which guaranteed those inalienable rights. He set down the policy of checks and balances later followed in the U.S. Constitution; formulated the doctrine that revolution in some circumstances is not only a right but an obligation; and argued for broad religious freedom.
His Two Treatises on Government supplied the classical statement of Whig theory and enjoyed great influence in America and France. It supposed that governments derive their authority from popular consent (regarded as a 'contract'), so that a government may be rightly overthrown if it infringes such fundamental rights of the people as religious freedom.
Sources:
http://ukdb.web.aol.com/hutchinson/encyclopedia/60/M0002060.htm
http://www.gis.net/~kingsley/locke-6.htm