John Locke was a 17th-century English philosopher whose ideas formed the foundation of liberal democracy and greatly influenced both the American and French revolutions. His contributions to philosophy include the theory of knowledge known as empiricism, which addressed the limits of what we can understand about the nature of reality. Locke held that our understanding of reality ultimately derives from what we have experienced through the senses. The political implications of his theories included the notions that all people are born equal and that education can free people from the subjugation of tyranny. Locke also believed that government had a moral obligation to guarantee that individuals always retained sovereignty over their own rights, including ownership of property that resulted from their own labor.
Politically active, Locke was personal physician and advisor to Anthony Ashley Cooper, the Earl of Shaftesbury, a leader in the parliamentary opposition to King Charles II. In 1681 Shaftesbury was accused of conspiring to overthrow Charles and was tried for treason. Although acquitted, he fled to the Netherlands and Locke followed. Locke stayed in exile until 1689, during which time he wrote his masterpiece, Essay Concerning Human Understanding, and actively plotted to put William of Orange on the English throne. Locke returned to England after King James II fled and William was crowned William III (in the turn of events known as the Glorious Revolution). Over the next several years he published his most important works, including A Letter Concerning Toleration (1689), Two Treatises on Government (1690) and Some Thoughts Concerning Education (1693).