No interpretation of the Tractatus can be adequate unless it reconciles two central themes of the work. The first is the Grundgedanke (fundamental idea) of the Tractatus. Wittgenstein states it as follows (TLP 4.03):
My fundamental idea is that the ‘logical constants’ are not representatives; that there can be no representatives of the logic of facts.
The fundamental idea, by its name alone, has rights to being the focal point of the Tractatus. The second central theme is the Doctrine of Showing. In a letter to Russell of 1919, Wittgenstein responded to some questions Russell had raised about the Tractatus. He writes:
Now I'm afraid you haven't really got hold of my main contention, to which the whole business of logical propositions is only corollary. The main point is the theory of what can be expressed (gesagt) by propositions – i.e., by language (and, what comes to the same, what can be thought) and what cannot be expressed by propositions, but only shown (gezeigt); which, I believe, is the cardinal problem of philosophy.
Wittgenstein's letter says that distinction between showing and saying is the “main contention” of the work. These two themes must somehow be fit together.
On Anscombe's interpretation, the “picture theory of meaning” is the central principle of the Tractatus. Both Showing and the fundamental idea are subsumed under it.