An English philosopher and political theorist, and one of the precursors of the Enlightenment. He took an interest in numerous disciplines: philosophy, politics, as well as medicine, physics and chemistry. His opposition to absolutist politics under the Stuart monarchy obliged him to go into lengthy exile in France and then the Netherlands. He only returned to England after the Revolution of 1688. From a philosophy perspective Locke was the first major representative of Anglo-Saxon empiricism. In his Essay Concerning Human Understanding (1690), he set out to demonstrate how ideas are formed and how knowledge is constituted, essentially on the basis of tangible experience. His opposition to absolutism and his taking a position in favour of the separation of the powers made him one of the founders of political liberalism. Favourable to a constitutional monarchy, he considered that society should be founded on a contract. But if the sovereign abuses his rights, insurrection is legitimate (A Letter Concerning Toleration, 1689). Locke’s influence on the thought of the 18th century thought and beyond would be considerable, as well as on the emergence of the concept of a state run through the rule of law.