The Concept of Mind is a 1949 book by philosopher Gilbert Ryle, in which the author 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. Ghost in the machine In the chapter "Descartes' Myth", Ryle introduces "the dogma of the Ghost in the machine" to describe the philosophical concept of the mind as an entity separate from the body:I hope to prove that it is entirely false, and false not in detail but in principle. It is not merely an assemblage of particular mistakes. It is one big mistake and a mistake of a special kind. It is, namely, a category mistake. Critique of Cartesian dualism Ryle rejects Descartes' theory of the relation between mind and body, on the grounds that it approaches the investigation of mental processes as if they could be isolated from physical processes. In order to demonstrate how this theory may be misleading, he explains that knowing how to perform an act skillfully may not only be a matter of being able to reason practically but may also be a matter of being able to put practical reasoning into action. Practical actions may not necessarily be produced by highly theoretical reasoning or by complex sequences of intellectual operations. The meaning of actions may not be explained by making inferences about hidden mental processes, but it may be explained by examining the rules that govern those actions. According to Ryle, mental processes are merely intelligent acts. There are no mental processes that are distinct from intelligent acts. The operations of the mind are not merely represented by intelligent acts, they are the same as those intelligent acts. Thus, acts of learning, remembering, imagining, knowing, or willing are not merely clues to hidden mental processes or to complex sequences of intellectual operations, they are the way in which those mental processes or intellectual operations are defined. Logical propositions are not merely clues to modes of reasoning, they are those modes of reasoning. The rationalist theory that there is a transformation into physical acts of some purely mental faculty