In the opening pages of the Tractatus, 1 Wittgenstein presents a striking metaphysics—or metaphysical picture—that seeks to convey a conception of the world as ‘the totality of facts’. In the course of these remarks there occurs an argument—or at least the appearance of an argument—for the enigmatic thesis that ‘the world has substance’: 2.0211 If the world had no substance, then whether a proposition had sense would depend on whether another proposition was true. 2.0212 It would then be impossible to draw up a picture of the world (true or false). This brief argument has presented an abiding challenge to Wittgenstein’s interpreters. One of its many mysteries concerns its invocation of the notion of substance. Because ‘objects form the substance of the world’ (2.021), the argument must be intended to establish the existence of Tractarian objects. But since that is so, why doesn’t Wittgenstein argue directly for objects? Why does he introduce the concept of substance at all? This question forms the point of departure for the present essay. The answer, I shall claim, is that in portraying objects as comprising ‘the substance of the world’ Wittgenstein means to be exploiting the reader’s presumed familiarity with the philosophical tradition. Specifically, he is alluding to Kant’s conception of substance as that which persists through all existence changes. The allusion, I take it, is intended to convey some (partial and provisional) understanding of the notion of a Tractarian ‘object’. The reader who picks up on it will be able to follow Wittgenstein along as he traces the metaphysical picture he intends, later in the book, to undermine. I shall argue that proceeding on the assumption of a Kantian allusion sheds much light both on the argument for substance itself and on Wittgenstein’s socalled ‘ontological remarks’ at the beginning of the Tractatus. It will emerge that in contending for substance Wittgenstein is arguing not merely for the existence of simple things, but for things that exist necessarily. Moreover, certain (relatively coarse-grained) instabilities and tensions that commentators have discerned in Wittgenstein’s talk of ‘objects’ and ‘configurations’ will be shown to be resoluble so long as the Kantian background is kept firmly in mind. In what follows, I will be defending an interpretation according to which Tractarian substance is the modal analogue of Kant’s (temporal) notion. Having made this case, I will offer my own interpretation and evaluation of the argument