John Locke was an influential 17th-century English philosopher, often regarded as the father of liberalism. He is best known for his theories of the mind and knowledge, articulated in works such as "An Essay Concerning Human Understanding," where he proposed the idea of the mind as a "tabula rasa" or blank slate. Locke's political philosophy, articulated in "Two Treatises of Government," emphasized the social contract and the rights to life, liberty, and property, profoundly influencing modern political thought and documents like the U.S.