The text of The Tractatus supports incompatible interpretations of a number of key philosophic positions. For example, the book is neither obviously nominalistic nor obviously realistic. Another difficulty is presented by the apparent . incompatibility of Wittgenstein's theses (1) that propositions are logical pictures of facts, and (2) that propositions are truth-functions of elementary propositions. There are several places in The Tractatus where these two doctrines meet head on, but the central one is the set of passages 5.54-5.5422. This paper is an exegesis of these passages and a sketch of Wittgenstein's theory of judgement.
In Tractatus 5.54 - 5.5422, Wittgenstein argues that statements of belief, judgement, thoughts and the like are not incompatible with the principle of finite extensionality. The passages contain a brief but obscure reductio on the possibility of non-extensional contexts, and several no less obscure corollaries. In this paper I shall explicate the content of the reductio, criticise a common but mistaken view of these passages, and draw out the consequences of some major doctrines in the Tractatus for Wittgenstein's Theory of Judgement.