2.161 In the picture and the depicted there must be something identical so that one can be a picture of the other at all.
This might sound reasonable, but what does, say, "The cat sat on the mat" have in common with a cat's sitting on a mat? What is identical in the pictured and the picture? Perhaps we could say what is identical is a certain relation that they share. Otherwise nothing comes to mind. And remember we have not yet been given any examples of pictures. Are they literal pictures, as one might reasonably think? Or sentences, as is often thought? Or propositions? And how are we to decide exactly how they relate to "states of affairs" (whatever exactly they might be)?
Ostrow (p. 39) says of standard interpretations that: “Wittgenstein’s answer to the question of how the picture – and hence language – can always be about the world is thus supposedly to be: they share a form.” And yet: “the strategy of taking recourse in talk of an isomorphism is empty; it amounts to no more than the claim that depicting the world is possible because the world has the possibility of being depicted.”