What Is a Category Mistake? Asking a Question That Cannot Have an Answer
By the BrainSnail editorial team. How these articles are written and checked, and how to tell us when one is wrong.
Some questions are not hard but malformed, treating something as if it belonged to a category it does not belong to. Asking what colour Thursday is produces no answer, not because the answer is unknown but because days are not the kind of thing that has a colour.
The visitor and the university
The philosopher Gilbert Ryle introduced the term in 1949 with an example that has been repeated ever since. A visitor is shown around a university, sees the colleges, the libraries, the laboratories, the playing fields and the administrative offices, and then asks where the university is. The visitor has mistakenly assumed that the university is another institution of the same kind as the colleges and libraries, to be found alongside them, when it is the way in which those things are organised. The question is not difficult to answer, it is confused, and the correct response is to explain the error rather than to search for a missing building. Ryle offered further examples, including a spectator at a parade asking when the division will appear after watching the battalions, batteries and squadrons pass, and the point in each is that words can belong to different logical categories while looking grammatically parallel, so a perfectly well-formed sentence can express an incoherent thought.
What Ryle was arguing against
The concept was not introduced for its own sake but as a weapon against a particular philosophical position:
- •The Cartesian view that mind and body are two distinct substances, one physical and one not, interacting somehow
- •Ryle's claim that this treats the mind as a thing of the same logical type as the body, which is exactly the visitor's error transferred to a person
- •His alternative that mental terms describe dispositions to behave rather than inner episodes in a private theatre, so being intelligent is a way of doing things rather than a hidden process accompanying them
- •The phrase he coined for the position he rejected, describing it as the ghost in the machine, which passed into general use largely detached from his argument
- •The behaviourist reading of his view, which he denied and which critics pressed anyway, and which has been the main line of objection since
- •The lasting influence of the diagnosis regardless of whether his positive account succeeded, since the idea that some philosophical problems are conceptual confusions rather than open questions became widespread
How to spot one
The practical test is whether the predicate can apply to the subject at all, rather than whether it happens to be true. Numbers do not have weight, so asking whether seven is heavy is not false but nonsensical. Legal persons and natural persons share a word and not every property, which is why arguments about corporate responsibility frequently founder. A common source of trouble is the part and the whole, where properties of components are wrongly attributed to the assembly or the reverse, and the fallacies of composition and division are close relatives of the category mistake. Another is the treatment of processes as objects, so asking where the mind is located, where a habit is stored or what the economy wants can generate confusion of exactly this kind. The diagnosis is contestable and frequently contested, since claiming that an opponent has made a category mistake is a strong move that dismisses their question rather than answering it, and it can be used to avoid a genuine problem by declaring it meaningless.
Where it still bites
Several live debates turn partly on whether one is being made. Asking whether a computer can think is treated by some as a straightforward empirical question and by others as a category mistake resting on a misuse of a word whose home is in describing whole living creatures. Questions about whether a brain scan shows a decision or merely correlates with one raise similar issues about attributing to parts what belongs to persons, and several philosophers have argued at length that neuroscience routinely commits this error in its language. Debates about consciousness frequently divide between those who see a hard problem requiring explanation and those who see a conceptual confusion generating a pseudo-problem. Asking what caused the universe, if time began with it, may be malformed in the same way. In each case the disagreement is not about facts but about whether the question is well posed, which is uncomfortable because there is no agreed procedure for settling that, and one side's dissolution of a problem is the other side's evasion of it.
The takeaway
A question can be malformed rather than hard, treating something as the kind of thing it is not, which is why asking where the university is after seeing every college gets an explanation rather than an answer. Ryle introduced it in 1949 to attack the idea of mind as a separate substance. Claiming an opponent has made one is a strong move, since it dismisses the question rather than answering it, and can be used to dodge real problems.