On the Category Error

Back from a very busy summer, let’s do some philosophy again: To demolish your friends’ arguments, point out their category errors to them, and watch your circle of friends dwindle.


One of the commonest errors that people commit when discussing various philosophical, cultural, and social issues with one another, is the category error (which should not be confused with a “categorical error”, although they are sometimes used interchangeably, since “categorical” can mean unequivocal, direct, or unconditional, whereas a category error involves actual categories). The notion of a category is extremely important in philosophy, which is why already Aristotle made sure to discuss it in his Metaphysics. By saying “Socrates” I refer to Socrates; when I say “Socrates is a man”, I introduce an example of a category that includes items that are not Socrates. How do those items help me understand the first reference, namely Socrates? Aristotle introduces several “super-categories”, including substance, quality, quantity, relation, action, place, etc. Understanding categories helps us understand reality, the objects with which we interact, and the situations in which we find ourselves.

The inestimable Ryle, who not only showed that much of Descartes is rubbish (if it wasn't evident already), but also helped fight the Nazis by serving in linguistic intelligence.

The idea of the category error, sometimes known as the category mistake, was initially introduced by the British philosopher of language Gilbert Ryle in his book The Concept of Mind (1949), as part of his attack on Cartesian dualism (an effort I wholeheartedly support, but that is another story). The category error has since then broadened somewhat to mean the following: an error that occurs when someone presents objects belonging to one category as belonging to another, or when someone puts objects in the same category when in fact they belong in different categories. This might sound fairly technical, but it is in fact a mistake that people commit all the time without being aware of it, and which invalidates their arguments.

A stock example offered by Ryle himself is when someone asks to see the university in Oxford, and is shown the buildings, the students, and the professors. The person acknowledges that he can see the buildings, the students, and the professors, but wonders where the university itself is, not realizing that “university” is an abstraction composed of the buildings, the students, the professors etc. We can conclude from this that the person places “university” and e.g. “student” in the same category, as two things of the same type that can therefore be compared with each other, whereas in fact they cannot be thus compared. The person has committed a category error. 

A typical category error (illustration by Grayson Perry).

Another example can be seen in the image to the left. The visitors in the art gallery treat politics, ideas, and humor as belonging to some category other than art. By “art” they seem to mean something like “skill”. Even though it is true that the etymological meaning of the word “art” is in fact “skill” (from the Latin ars, meaning precisely skill or craft), today we use the word art as a much more complex abstraction, which can include elements of humor, politics, and various other ideas. So what the viewers consider to be positive (“lovely politics”, “great idea”, “very funny”) are precisely the things that form part of the art itself, and so the conclusion “shit art”, as separate from the humor and the politics, is false.

In these examples of the university and of art, the error is fairly obvious; in other cases it is less so, but still easily identifiable to anyone who is aware of the notion of category error and has become used to spotting it. In the quote to the right, the fairly talentless comedian in question commits a definite category error. This one is perhaps slightly more difficult to spot, since it deals more with concrete things (shoes, bombs, guns), as opposed to a clear division between concrete and abstract (student, university), but the category error is nonetheless unmistakable: The attempt of hiding a bomb in a shoe has led to the policy of passengers having to remove their shoes at airports to show that there are no bombs in their footwear; so too school shootings should lead – so he implicitly states – to a regulation of guns, but it has not. In reality, of course, the regulation of shoes falls into a very different category than the regulation of guns, because people do not fear the shoe but rather the bomb that could be put into it. The proper comparison should thus be not between guns and shoe removal – and additionally, the former is an object and the latter is an event – but between guns and bombs, and bombs are in fact illegal at airports (and in most other places, even more so, in fact, than guns). Someone might perhaps argue that the comparison being made is between the regulation of bombs and the regulation of guns, but even then the category of place enters the picture: Both bombs and guns are in fact illegal in airports. One might say that since the individual who came up with this statement is a comedian, one should not take the statement too seriously, but this and similar statements are in fact taken very seriously by an awful lot of people, people who have not studied any philosophy and who do not have a proper enough understanding of their own language to deal with its concepts in a competent manner. That is to say, they handle the concepts of their language improperly by confusing various logical types.