4.0312 The possibility of a proposition is based on the principle of the representation of objects by signs.

My fundamental thought is that the “logical constants” represent nothing. That the logic of facts does not allow of representation.

Mounce (p. 12) says of this “fundamental idea” that: “logic … reflects, on Wittgenstein’s view, by showing not by saying. This indeed is the central doctrine of the Tractatus. Logic differs from all the other sciences because the other sciences say something about the world whereas logic only shows something.” There is no representation, but there is reflection, in other words.

Ostrow (p. 87): “We are meant to see that, contrary to Frege’s contention, the logical functions cannot be construed along the lines of genuine (material) functions, that it makes no sense to suppose a domain of entities which form the special province of the logician. Nor is this a point directed merely at Frege. Russell is even more explicitly committed to the assumption of a definite logical subject matter, as is evident in his … claim that “the chief part of philosophical logic” is “the endeavor to see clearly the entities” that mathematics regards as indefinable (Principles xv).” On this, see note to 2.01. In Letters to Ogden p. 20, Wittgenstein rejects the suggested title for the TLP of Philosophic Logic saying that this title would be “wrong. In fact I don’t know what it means! There is no such thing as philosophic logic.” It seems clear that his objection was not merely that it should be Philosophical Logic instead.

My initial reaction: The fundamental idea. This must be important. So, there being propositions depends on the principle that objects can be replaced by signs that go proxy for them. But this principle seems to be false. Propositions are essentially representative in a way that objects are not. A cat sitting on a mat has no meaning. “The cat sat on the mat” has. And “The [picture of a cat] sat on the ___" has no meaning at all, although you might guess what I have in mind. Objects are not replaced by signs. They are represented by them, which is quite a different thing. Let’s assume that this is what Wittgenstein means. Propositions depend on the representation of objects, not of the logic of facts. But weren’t objects something like possibility points? And isn’t logic all about possibility? Maybe the logic of objects can be represented but not the logic of facts. But facts are made of objects, so why should there be a difference? This is a little obscure. Perhaps though the implication is that propositions as described in the Tractatus really are not possible.