Page:Wittgenstein - Tractatus Logico-Philosophicus, 1922.djvu/55

Rh same way. Names cannot be taken to pieces by definition (nor any sign which alone and independently has a meaning).

What does not get expressed in the sign is shown by its application. What the signs conceal, their application declares.

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.

Only the proposition has sense; only in the context of a proposition has a name meaning.

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.

An expression characterizes a form and a content.

An expression presupposes the forms of all propositions in which it can occur. It is the common characteristic mark of a class of propositions.

It is therefore represented by the general form of the propositions which it characterizes.

And in this form the expression is constant and everything else variable.

An expression is thus presented by a variable, whose values are the propositions which contain the expression.

(In the limiting case the variable becomes constant, the expression a proposition.)

I call such a variable a “propositional variable”.

An expression has meaning only in a proposition. Every variable can be conceived as a propositional variable. Rh