An Essay Concerning Human Understanding is a work by John Locke concerning the foundation of human knowledge and understanding. Locke describes the mind at birth as a blank slate (tabula rasa, although he did not use those actual words) filled later through experience. A dominant theme of the Essay is the question: What is the capacity of the human mind for understanding and knowledge? The Essay’s influence was enormous, perhaps as great as that of any other philosophical work apart from those of Plato and Aristotle. Its importance in the English-speaking world of the 18th century can scarcely be overstated. Along with the works of Descartes, it constitutes the foundation of modern Western philosophy.