During his decades of service to Shaftesbury, John Locke had been writing. In the six years following his return to England he published all of his most significant works.
Locke’s “Essay Concerning Human Understanding” (1689) outlined a theory of human knowledge, identity and selfhood. To Locke, knowledge was not the discovery of anything either innate or outside of the individual, but simply the accumulation of “facts” derived from sensory experience. To discover truths beyond the realm of basic experience, Locke suggested an approach modeled on the rigorous methods of experimental science.
The “Two Treatises of Government” (1690) offered political theories developed and refined by Locke during his years at Shaftesbury’s side. Rejecting the divine right of kings, Locke said that societies form governments by mutual (and, in later generations, tacit) agreement. Thus, when a king loses the consent of the governed, a society may remove him—an approach quoted almost verbatim in Thomas Jefferson’s 1776 Declaration of Independence. Locke also developed a definition of property as the product of a person’s labor that would be foundational for both Adam Smith’s capitalism and Karl Marx’s socialism.
In his “Thoughts Concerning Education” (1693), Locke argued for a broadened syllabus and better treatment of students—ideas that were an enormous influence on Jean-Jacques Rousseau’s novel “Emile” (1762).
In three “Letters Concerning Toleration” (1689-92), Locke suggested that governments should respect freedom of religion except when the dissenting belief was a threat to public order. Atheists (whose oaths could not be trusted) and Catholics (who owed allegiance to an external ruler) were thus excluded from his scheme. Even within its limitations, Locke’s toleration did not argue that all (Protestant) beliefs were equally good or true, but simply that governments were not in a position to decide which one was correct.
Locke spent his final 14 years in Essex at the home of Sir Francis Masham and his wife, the philosopher Lady Damaris Cudworth Masham. He died there on October 24, 1704, as Lady Damaris read to him from the Psalms.