The term "category mistake" was introduced by Gilbert Ryle in his book The Concept of Mind to demonstrate what he believed was a confusion in the philosophy of mind introduced by Cartesian metaphysics. A category mistake is a semantic or ontological error where a thing is included in a category or set to which it does not belong. Ryle wrote:
When two terms belong to the same category, it is proper to construct conjunctive propositions embodying them. Thus a purchaser may say that he bought a left-hand glove and a right- hand glove, but not that he bought a left-hand glove, a right- hand glove, and a pair of gloves. ‘She came home in a flood of tears and a sedan-chair’ is a well known joke based on the absurdity of conjoining terms of different types. Now the dogma of the Ghost in the Machine does just this. It maintains that there exist both bodies and minds.[1]
Here, it is a category mistake to speak of a "pair of gloves" as if in the same category of the left and right hand gloves. A pair of gloves is in a different logical category than constituent parts of a pair. Ryle believed the classical theory of mind makes a similar "category mistake" by approaching "mind" and "body" as terms in the same logical category.
