category mistake the placing of an entity in the wrong category. In one of Ryle’s examples, to place the activity of exhibiting team spirit in the same class with the activities of pitching, batting, and catching is to make a category mistake; exhibiting team spirit is not a special function like pitching or batting but instead a way those special functions are performed. A second use of ‘category mistake’ is to refer to the attribution to an entity of a property which that entity cannot have (not merely does not happen to have), as in ‘This memory is violet’ or, to use an example from Carnap, ‘Caesar is a prime number’. These two kinds of category mistake may seem different, but both involve misunderstandings of the natures of the things being talked about. It is thought that they go beyond simple error or ordinary mistakes, as when one attributes a property to a thing which that thing could have but does not have, since category mistakes involve attributions of properties (e.g., being a special function) to things (e.g., team spirit) that those things cannot have. According to Ryle, the test for category differences depends on whether replacement of one expression for another in the same sentence results in a type of unintelligibility that he calls ‘absurdity.’ See also RYLE. J.W.M.