John Locke. Engraving of the English philosopher John Locke (1632-1704). Locke spent his early years lecturing at Oxford University, England. He later spent fifteen years in France where he met most of the leading continental scientists and thinkers. On his return, Locke published his Essay Concerning Human Understanding (1690). In this, he ventured that a person's mind was a tabula rasa or blank slate at birth. On this slate knowledge was imprinted by experience. The essay also argues that the proper basis of knowledge is experiment. In the same year he published his Two Treaties on Civil Government in which he attacked the divine right of kings and nature of the state.