of this principle? There has been a great deal of dispute about this question in modern philosophy, and certainly it deserves our full attention, for if I am not mistaken it is the fundamental principle of philosophizing, and neglect of it is the cause of all serious troubles in metaphysics.
The object of every proposition is to express a fact. It seems, then, that in order to state the meaning of the proposition we have to indicate the fact which it expresses. But how strange ! Is not the fact in question already indicated by the proposition itself? In fact, we have convinced ourselves long ago (see above p. 6 f) that a proposition expresses its own meaning, it does not stand in need of an explanation. An explanation which said more than the proposition itself would not be a correct explanation of it, and if it said the same thing as the proposition it would be superfluous. As a matter of fact, when we hear somebody make a statement and ask him "What do you mean by it?" we usually get and expect as an answer a mere repetition of the first statement, only in different words, and very often we are actually satisfied by this procedure which is nothing but a translation from one language into another one. Why are we satisfied? Evidently because we did not understand the first expression, but do understand the second one.
This last remark gives us the clue to solve the paradox. We can ask for a meaning only as long as we have not understood a statement. And as long as we have not understood a sentence it is actually nothing but a series of words; it would be misleading to call it a proposition at all. A series of words (or other signs) should be regarded as a proposition only when it is understood, when its meaning is comprehended. If we agree to use our terms in this way there will be no sense in asking for the meaning of a proposition, but we may very well inquire (and that was our actual problem) after the meaning of a sentence or any complex of signs which we suppose to express something.
Now there is not the slightest mystery about the process by which a sentence is given meaning or turned into a proposition: it consists in defining the use of the symbols which occur in the sentence. And this is always done by indicating the exact circumstances in which the words, according to the rules of the particular language, should be used. These rules must be taught by actually applying them in definite situations, that is to say, the circumstances to which they fit must actually be shown. It
