I believe that Gilbert Ryle introduced the term "category mistake", but I am struggling to apply the term.

Could you please give me an obvious and less obvious instance of a category-mistake?

And if something is a "category mistake" then what does that tell us about how to think about it?

  • An example is given here: rationalwiki.org/wiki/Category_mistake
    – user2953
    May 14, 2015 at 21:46
  • 1
    I would just like to add that in my personal experience, most category mistakes are due to strong misleading associations rather than, as in Wikipedia's (and the original term creator's) examples, arbitrary misunderstandings. For example, many people have turned out to, independently, believe that MSPaint, a bitmap drawing program, can't present photographs. Just because they've associated it with simple-looking drawings or, at most, screenshots. May 14, 2015 at 21:46

2 Answers 2


A category mistake is when, for the ontology of any particular domain of discourse, an element of a set is unjustifiably excluded from the set.

An obvious example of this is the statement, "It is a time before time". Time cannot be before time because the extension of time includes the extension of every statement of something being before or after something else (i.e. every B-series statement) such that "a time before time" falsely excludes "time" from the extension of "time".

A less obvious example is the statement, "It is before time", however this statement has similar problems to the one before because it is to say, "It is at an earlier point in time than time." This falsely excludes a point in time from time, which is false by contradiction.


The most common category errors generally go by separate names with which most folks are more familiar. Included are things like

  • anachronism,
  • anthropomorphizing,
  • taking a general principle personally,
  • attributing moral value to facts,
  • confusing the map with the terrain and
  • concretizing metaphors.

You can get the definition from the family resemblance between these examples: They involve lifting a property that needs a given context out of that context and presuming it has a value where it doesn't belong. Green ideas are not an oxymoron, they are a category mistake.

Anachronism is an example that is simple because it is so extreme. "When there were no clocks it must have been quite hard to catch a train." -- We are attributing modern intentions to ancient people, the need to catch a train is a property that those living before clocks just didn't have.

More subtle category errors common in our world right now include things like failing to see that faith in natural law is in fact faith because it is part of science and not religion or accepting success at Capitalism or some (other?) sport as the basis for one's judgment of someone's moral character.

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