on this, that it is not the same thing to change in quantity and in quality. Grant that in quantity a thing is not constant; still it is in respect of its form that we know each thing. — And again, it would be fair to criticize those who hold this view for asserting about the whole material universe what they saw only in a minority even of sensible things. For only that region of the sensible world which immediately surrounds us is always in process of destruction and generation; but this is — so to speak — not even a fraction of the whole, so that it would have been juster to acquit this part of the world because of the other part, than to condemn the other because of this. And again, obviously we shall make to them also the same reply that we made before;[1] we must show them and persuade them that there is something whose nature is changeless. Indeed, from the assertion that things at the same time are and are not, there follows the assertion that all things are at rest rather than that they are in movement; for there is nothing into which they can change, since all attributes belong already to all subjects.
Regarding the nature of truth, we must maintain that not everything which appears is true. Firstly, they contend that sensation — at least of the object peculiar to the sense in question — is not false; we answer that appearance is not the same as sensation. — Again, it is fair to express surprise at our opponents for raising the question whether magnitudes are as great, and colours are of such a nature, as they appear to people at a distance, or as they appear to those close at hand, and whether they are such as they appear to the sick or to the healthy, and whether those things are heavy which appear so to the weak or those which appear so to the strong, and whether truth is what appears to the sleeping or to the waking. For obviously they do not think these to be open questions; no one, at least, if when he is in Libya he fancies one night that he is in Athens, straightway starts for the Odeum. And again with regard to the future, as Plato says,[2] surely the opinion of the physician and that of the ignorant man are not equally weighty, for instance, on the question whether a man will get well or not. — And again, among sensa
