There's ambiguity in how you interpret a category error.
- “Nothing” as answer: the question is well-formed, it’s just that zero things satisfy the predicate. “How many
kings of France are there currently?” → zero. The question made sense, reality happened to supply nothing.- “Nothing” as dissolution: the question is malformed; the relation doesn’t apply at all, so asking for “what
satisfies it” is a grammatical confusion rather than a query about reality.You either choose to say that there is no “set of all sets” – nothing is the answer, or you can say it’s undefined (and alternatively have a class of all sets).
