 Regimented theory is, of course, an idealization. It is not a complete and finished object, available for us to examine. Quine’s reflections on it might be considered as something like a thought-experiment: if we were to set about assembling our total theory of the world and recasting it in the best form, what would it look like? Since the enterprise is not in fact going to be carried out all the way we are not going to get a detailed answer. But on some important general issues, Quine holds, we can get answers. In particular, he argues that the framework of regimented theory is first-order logic with identity (and so that theory is extensional); that the variables of this theory range only over physical objects and sets; and that the predicates of the theory, the only non-logical vocabulary, are physicalistic, in his somewhat complicated sense. (See section 5, below.) Although this is not traditional a priori metaphysics, we should not underestimate the ambition of the project. He says of his regimented theory that “all traits of reality worthy of the name can be set down in an idiom of this austere form if in any idiom” (1960, 228) and speaks of “limning the true and ultimate structure of reality” (1960, 221). The claim that the variables of regimented theory range only over physical objects and sets is, as far as he is concerned, the claim that only physical objects and sets really exist.