Logical Form - What can be shown, cannot be said.

Propositions must have logical form in common with reality in order to be able to describe anything real. But one cannot use propositions to describe logical form. In order to do that, one would need to be located somewhere outside of logic, that is to say outside the world. A proposition cannot exhibit a logical form because the form is reflected in it.

Language cannot describe what is reflected in it. We cannot express by means of language what expresses itself in our use of it. Propositions show the logical form of reality: They exhibit it.

Thus, the single proposition (fa) shows that object 'a' occurs in its sense. The two propositions (fa) and (ga) show that the same object is mentioned in both of them. If two propositions contradict one another, then their structure will show it. The same is true if one of them follows from the other, and so on. This explains our conviction that a logical conception is valid once we have the formalism right.

What can be shown, cannot be said.