But the attempt to close a mental process in an arbitrary manner is vain, and of necessity causes remorse and self-criticism. Thus it comes about, that each one of those unilateral and erroneous doctrines continually tends to surpass itself and to enter the stage which follows it. Thus empiricism, for example, assumes that it can dispense with any philosophical conception of art; but, since it severs art from non-art--and, however empirical it be, it will not identify a pen-and-ink sketch and a table of logarithms, as if they were just the same thing, or a painting and milk or blood (although milk and blood both possess colour)--thus empiricism too must at last resort to some kind of philosophical concept. Therefore, we see the empiricists becoming, turn and turn about, hedonists, moralists, intellectualists, agnostics, mystics, and sometimes they are even better than mystics, upholding an excellent conception of art, which can only be found fault with because introduced surreptitiously and without justification. If they do not make that progress, it is impossible for them to speak in any way of aesthetic facts. They must return, as regards such facts, to that indifference and to that silence from which they had emerged when they affirmed the existence of these facts and began to consider them in their variety. The same may be said of all other unilateral doctrines. They are all reduced to the alternative of advancing or of going back, and in so far as they do not wish to do either, they live amid contradictions and in anguish. But they do free themselves from these, more or less slowly, and thus are compelled to advance, more or less slowly. And here we discover why it is so difficult, and indeed impossible, exactly to identify thinkers, philosophers, and writers with one or the other of the doctrines which we have enunciated, because each one of them rebels when he finds himself limited to one of those categories, and it seems to him that he is shut up in prison. It is precisely because those thinkers try to shut themselves up in a unilateral doctrine, that they do not succeed, and that they take a step, now in one direction, now in another, and are conscious of being now on this side, now on the other, of the criticisms which are addressed to them. But the critics fulfil their duty by putting them in prison, thus throwing into relief the absurdity into which they are led by their irresolution, or their resolution not to resolve.