John Locke was an English philosopher and physician, widely regarded as one of the most influential Enlightenment thinkers. His work on social contract theory and the 'natural rights' of life, liberty, and property profoundly influenced the American Declaration of Independence and the U.S. Constitution. In 'Two Treatises of Government,' he argued against the divine right of kings and suggested that the legitimacy of a government comes from the consent of the governed. He also pioneered the concept of 'tabula rasa' (blank slate), suggesting that individuals are born without innate ideas and that knowledge is determined by experience and perception.