John Locke

Locke was born in the west of England to a Puritan lawyer who fought for Parliament in the Civil War. At Oxford he disliked scholasticism and turned to medicine and experimental science, working with Boyle and Sydenham. In 1666 he met the Earl of Shaftesbury, performed a successful operation on his liver, and became his physician, secretary and political adviser, drawn into the Whig struggle against the Stuarts.

After Shaftesbury's fall in 1683 Locke fled to Holland, where in exile he finished the Essay Concerning Human Understanding. He returned to England with Queen Mary's fleet after the Glorious Revolution of 1688, published the Two Treatises of Government anonymously the next year, the Letter Concerning Toleration the same year, and the Essay in 1690. He spent his last years at friends' house in Essex, advising on the recoinage and corresponding with Newton.

The Essay denies innate ideas: the mind is born a blank sheet, and all ideas come from sensation and reflection. Simple ideas combine into complex ones; a body's primary qualities (shape, motion) really exist in it, while secondary qualities (colour, smell) are only the sensations they cause in us. The Two Treatises hold that in the state of nature people are free and equal with rights to life, liberty and property, that government exists solely to protect those rights, and that when it violates them the people may resist. The American Declaration of Independence is almost a summary of the book.