The postulate of the possibility of the simple signs is the postulate of the determinateness of the sense.
3.24
A proposition about a complex stands in internal relation to the proposition about its constituent part.
A complex can only be given by its description, and this will either be right or wrong. The proposition in which there is mention of a complex, if this does not exist, becomes not nonsense but simply false.
That a propositional element signifies a complex can be seen from an indeterminateness in the propositions in which it occurs. We know that everything is not yet determined by this proposition. (The notation for generality contains a prototype.)
The combination of the symbols of a complex in a simple symbol can be expressed by a definition.
3.25
There is one and only one complete analysis of the proposition.
3.251
The proposition expresses what it expresses in a definite and clearly specifiable way: the proposition is articulate.
3.26
The name cannot be analysed further by any definition. It is a primitive sign.
3.261
Every defined sign signifies via those signs by which it is defined, and the definitions show the way.
Two signs, one a primitive sign, and one defined by primitive signs, cannot signify in the same way. Names cannot be taken to pieces by definition (nor any sign which alone and independently has a meaning).
3.262
What does not get expressed in the sign is shown by its application. What the signs conceal, their application declares.
3.263
The meanings of primitive signs can be explained by elucidations. Elucidations are propositions which contain the primitive signs. They can, therefore, only be understood when the meanings of these signs are already known.
3.3
Only the proposition has sense; only in the context of a proposition has a name meaning.
3.31
Every part of a proposition which characterizes its sense I call an expression (a symbol).
(The proposition itself is an expression.)
Expressions are everything—essential for the sense of the proposition—that propositions can have in common with one another.