An Essay Concerning Human Understanding is a work by John Locke concerning the foundation of human knowledge and understanding. It first appeared in 1689 (although dated 1690) with the printed title An Essay Concerning Humane Understanding. He describes the mind at birth as a blank slate (tabula rasa, although he did not use those actual words) filled later through experience. The essay was one of the principal sources of empiricism in modern philosophy, and influenced many enlightenment philosophers, such as David Hume and George Berkeley.