The General Propositional Form in Wittgenstein's Tractatus

As it was mentioned in the last article that we use the perceptible sign of a proposition as a projection of a possible situation (3.11) such as spatial relations. Wittgenstein emphasizes at 3.13 that:

A proposition, therefore, does not actually contain its sense, but does contain the possibility of expressing it. ("The content of a proposition" means the content of a proposition that has sense.) A proposition contains the form, but not the content, of its sense.

In addition, the general propositional form is the essence of a proposition (5.471). For all that are possible in logic, Wittgenstein says at 5.473 and 5.4733 that

If a sign is possible, then it is also capable of signifying. Whatever is possible in logic is also permitted. Any possible proposition is legitimately constructed.

He also gives the sentence "Socrates is identical" as an example of a possible proposition. This proposition is, therefore, not only legitimately constructed and permitted, but also capable of signifying. It has no sense just because we have failed to give a meaning to the sign "identical", even if we think that we have done so (5.4733). It is we who failed to use the perceptible sign of this proposition as a projection of a possible situation (3.11).