On Category Mistakes
In The Concept of Mind, Gilbert Ryle provides an amusing story to illustrate the meaning of ‘category mistake.’ Suppose that you take a friend to visit the local university. You schedule a tour of the campus which includes trips to the library, the buildings for the sciences and the humanities, the recreation center, the student advising offices, the administration buildings, etc. Near the end of the tour, your friend asks: “We’ve seen a lot of buildings, but I guess we haven’t seen them all yet. When will we see the university?” Your friend is making a category mistake. He doesn’t understand that the university is the whole of which the various buildings, offices, faculty, staff, their relations, etc., are parts. He expects the university to be one of the buildings to see on the tour. He mistakes whole for part.
There is a reverse of this mistake: mistaking part for whole. Suppose you see a charming house with colorful flowers in the front yard and a white picket fence. The house is located in a neighborhood which is partly attractive, partly average, and partly run-down. You take photographs of the house and show your friend, who likes them and asks you to take her next week to see the neighborhood. The day arrives, and you start your tour on a street which lacks charming houses. She is disappointed. You ask why. She responds: “This neighborhood is not like the photos you showed me!” Somehow, your friend had construed the pictures as indicative of the neighborhood as a whole. She saw an image of a small part of the neighborhood (i.e., a photograph of the house) and took it as a picture of the whole neighborhood.
The fallacies of composition and division are relevant here.