The thought is the significant proposition.
4.01 (6) The proposition is a picture of reality.
The proposition is a model of the reality as we think it is.
4.02 (7) This we see from the fact that we understand the sense of the propositional sign, without having had it explained to us.
4.03 (2) A proposition must communicate a new sense with old words.
The proposition communicates to us a state of affairs, therefore it must be essentially connected with the state of affairs.
And the connexion is, in fact, that it is its logical picture.
A proposition states something only in so far as it is a picture.
4.04 (1) In the proposition there must be exactly as many thing distinguishable as there are in the state of affairs, which it represents.
They must both possess the same logical (mathematical) multiplicity (cf. Hertz's Mechanics, on Dynamic Models).
4.05 Reality is compared with the proposition.
4.06 (4) Propositions can be true or false only by being pictures of the reality.