Book 4
6
To those, then, who base their judgement on these considerations, we shall say that although in one sense their theory is correct, in another they are mistaken. For being has two meanings, so that there is a sense in which something can be generated from not-being, and a sense in which it cannot; and a sense in which the same thing can at once be and not be; but not in the same respect. For the same thing can be contraries at the same time potentially, but not actually.
7
And further, we shall request them to conceive another kind also of substance of existing things, in which there is absolutely no motion or destruction or generation. And (2.) similarly the theory that there is truth in appearances has come to some people from an observation of sensible things.
8
They think that the truth should not be judged by the number or fewness of its upholders; and they say that the same thing seems sweet to some who taste it, and bitter to others; so that if all men were diseased or all insane, except two or three who were healthy or sane, the latter would seem to be diseased or insane, and not the others.
9
And further they say that many of the animals as well get from the same things impressions which are contrary to ours, and that the individual himself does not always think the same in matters of sense-perception. Thus it is uncertain which of these impressions are true or false; for one kind is no more true than another, but equally so. And hence Democritus saysCf. Ritter and Preller, 204. that either there is no truth or we cannot discover it.
10
And in general it is because they suppose that thought is sense-perception, and sense-perception physical alteration, that they say that the impression given through sense-perception is necessarily true; for it is on these grounds that both Empedocles and Democritus and practically all the rest have become obsessed by such opinions as these.
11
For Empedocles says that those who change their bodily condition change their thought:
