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A category mistake (or category error), a term coined by philosopher Gilbert Ryle, is a type of informal fallacy where things that belong to one grouping are mistakenly placed in another. The example Ryle gives is of someone visiting Oxford who looks around and asks to see the university. His guide tells him he is at the university; "Here are the buildings, here are the professors, here are the students, etc." The visitor then tells him that he sees the buildings, the professors, and the students, but he still doesn't see the university. The point of the story is that the visitor has the expectation that the university is a physical object and not an abstraction, but the two obviously belong to separate categories altogether. Ryle makes this distinction as an argument against dualism, but the idea of the category mistake has entered common philosophical parlance. As the example demonstrates, the category mistake is often tied into the fallacies of composition and division.