the transmission of a comparatively constant structure, or, still more correctly, it is a continuous series of events having approximately the same structures.
If (in the language of traditional metaphysics) I could take the greenness of a colrur which I am experiencing out of my own consciousness and put it into somebody else's, then he would have the green itself, and not an expression of it. We do not use the word "Expression" unless there is some other material which, as it were, carries the meaning of the expression, and this "other" excludes the original content. Expression involves some means of communication which does not (if it were at all possible) seize the fact or object itself, does not do anything to it, but leaves it entirely as it is and where it is, conveying to us only those of its features which it may share with other materials. I might be tempted to say: well, those features are the structure, and the rest (whether it be called "material" or otherwise) is Content, but such a figure of speech would be entirely misleading, as it seems to give an indirect description of content-which we know to be impossible. And I might be tempted to say that content cannot be expressed by language because the nature of language is expression, not transportation; but again this would give the wrong impression as if there were any sense in speaking of the transportation of content, and we know that there is not.
We can say that we express a fact by another fact (a sentence, a gesture, etc.), but to speak of expressing content is a contradiction in itself, like making music without sounds or painting without dyes. These things cannot be done not because they are too difficult and beyond human faculties, but because there are no such things: the sentences in which we seem to be speaking of them are meaningless in the same sense in which it is meaningless to speak of a "round square". (I need not remind the reader that the sentence "there is no round square" cannot be interpreted as asserting the non-existence of a certain thing called a round square, but must be understood as saying that the combination of words "round square" makes no sense.)
