Locke came from the non-Anglican Protestant community in England, learning as a child the virtues of Calvinist simplicity but little of the harsh, judgmental aspect of that sect. He was educated at Oxford University, but he moved away from the then-fashionable scholasticism and, under the influence of Robert Boyle, began to study practical science. He chose medicine as his specialty and worked with the famous Thomas Sydenham. He never took his degree or practiced medicine (the former was not required for the latter at that time), but the influence of his training would remain with him.
After completing a diplomatic mission in 1665, Locke returned to Oxford and immersed himself in the writings of René Descartes. Two years later, the Earl of Shaftesbury, a school friend, invited Locke to become his personal physician and live with him. Locke proved to be as much secretary as doctor, helping his patron with such projects as the Constitution for the Carolinas. He was also elected a fellow of the Royal Society.
In 1675, Locke began a long visit to France both for his health and to expand his study of Descartes. He returned home in 1679 only to face political problems when his patron, Shaftesbury, was accused of treason. Although he was acquitted, Shaftesbury fled to Holland in 1681, and Locke, who had held some minor government posts under Shaftesbury’s influence, found it best to follow his example. After Monmouth’s Rebellion (1685), Locke was branded a traitor, and the English government demanded his extradition. The Dutch paid little attention, and Locke lived quietly, continuing work on what was to be An Essay Concerning Human Understanding. He returned home after the Revolution of 1688 and increasingly divided his time between London, where he served as a commissioner of appeals, and Oates, the Essex home of his friends Sir Francis and Lady Masham. It was in this comfortable, supportive home that Locke, in the 1690’s, was at his most prolific, though his Essay and Two Treatises had been in development for years.