That's not what critical theorists think; for them, often the process of describing a phenomenon involves looking at how "it" behaves. The idea that everything must be defined analytically before it is used or analyzed shuts one off from a lot of possible insight. For example, the debate as to whether porn is art continues to this day, but we have analyzed both porn, art and porn as art before we were ever clear on the matter rigourously speaking. Furthermore, to impose a definition is to trap a concept (usually a historically contingent one) in a moment, which isn't always useful. There are some works on the matter of definitionalism that make this point better but I can't find them right now. I'm short, critical theory and philosophy are different sciences (another thorny word to define, but we use it regardless of the intellectual poverty of some of its widely accepted definitions) to mathematics.

Sure, I completely agree that a book discussing porn vs art can't literally start with definitions they way a math book can, that's too narrow.

But if it wishes to use an existing word like "art" in a new sense, for instance to claim that all portrayal of humans is inherently pornographic, then IMHO it needs to be very careful to distinguish this from pre-existing meanings. The fact that some building on campus has "art" chiseled into the marble cannot be assumed to already imply agreement with some new meaning you invented 5 pages ago, a meaning which would have been very surprising to the guys who sponsored the building.

Even if you ultimately make a convincing case that the sense you describe is somehow more correct/useful/interesting than other ones, or encompasses them, you've got to act as if you haven't yet shown that. That's what I meant he should have learned in math class. And really the more honest course is to introduce new words for new concepts, not to try to muddle older ones, as Said successfully did.

But, to be fair, I didn't finish the book.