Kyle's introduction of the topic. The matter is introduced by Ryle in his 1938 article in a sufficiently striking way. It is, he says, a matter of some importance, "for not only is it the case that category-propositions (namely, assertions that terms belong to certain categories or types) are always philosopher's propositions, but, I believe, the converse is also true. So we are in the dark about the nature of philosophical problems and methods if we are in the dark about types or categories."¹ In Philosophical Argument (1946) he seems, though less explicitly, committed to the same view. It appears again, robustly enough, in the Introduction to The Concept of Mind (1949): "Philosophy is the replacement of category-habits by category-disciplines."² It is echoed in his declaration, made in the first chapter of that work, that the "official theory" he is bent on destroying is "one big mistake … namely a category-mistake;"³ or, perhaps, a "family" or "batch" of category-mistakes.⁴