by an analogous arrangement of the relevant signs in sentences (which contain the same possibilities of combination as prescribed by logical syntax), hence logical form can only be shown by presenting the logical relations between different sentences. Wittgenstein's conception of representation as picturing also allows him to derive two striking claims: that no proposition can be known a priori – there are no apriori truths (TLP 3.05), and that there is only logical necessity (TLP 6.37). Since all propositions, by virtue of being pictures, have sense independently of anything being the case in reality, we cannot see from the proposition alone whether it is true (as would be the case if it could be known apriori), but we must compare it to reality in order to know that it is true (TLP 4.031 "In the proposition a state of affairs is, as it were, put together for the sake of experiment"). And for similar reasons, no proposition is necessarily true except in the limiting case of tautologies, which Wittgenstein say lack sense (TLP 4.461). If a proposition pictures a state of affairs in virtue of being a picture in logical space, then a non-logical or metaphysical "necessary truth" would be a state of affairs which is satisfied by any possible arrangement of objects (since it is true for any possible state of affairs), but this means that the would-be necessary proposition would not depict anything as being so but will be true no matter what the world is actually like; but if that's the case, then the proposition cannot say anything about the world or describe any fact in it – it would not be correlated with any particular state of affairs, just like a tautology (TLP 6.37). Logical atomism Although Wittgenstein did not use the term himself, his metaphysical view throughout the Tractatus is commonly referred to as logical atomism. While his logical atomism resembles that of Bertrand Russell, the two views are not strictly the same. Russell's theory of descriptions is a way of logically analyzing sentences containing definite descriptions without presupposing the existence of an object satisfying the description. According to the theory, a statement like "There is a man to my left" should be analyzed into: "There is some x such that x is a man and x is to my left, and for any y, if y is a man and y is to my