The Concept of Mind by philosopher Gilbert Ryle argues that "mind" is "a philosophical illusion hailing chiefly from René Descartes and sustained by logical errors and 'category mistakes' which have become habitual."The work has been cited as having "put the final nail in the coffin of Cartesian dualism," and has been seen as a founding document in the philosophy of mind, which received professional recognition as a distinct and important branch of philosophy only after 1950.This now-classic work challenges what Ryle calls philosophy's "official theory," the Cartesians "myth" of the separation of mind and matter. Ryle's linguistic analysis remaps the conceptual geography of mind. His plain language and essentially simple purpose place him in the traditioin of Locke, Berkeley, Mill, and Russell.