[20] The same will apply too if anyone posits more than one, as e.g. Empedocles says that matter consists of four bodies;objections must occur in his case also, some the same as before, and some peculiar to him. First, we can see things being generated from each other in a way which shows that fire and earth do not persist as the same corporeal entity. (This subject has been treated in my works on Natural Science.4) Again with regard to the cause of motion in things, whether one or two should be assumed, it must not be thought that his account is entirely correct or even reasonable.5And in general those who hold such views as these must of necessity do away with qualitative alteration; for on such a theory cold will not come from hot nor hot from cold, because to effect this there must be something which actually takes on these contrary qualities: some single element which becomes both fire and water—which Empedocles denies.
If one were to infer that Anaxagoras recognized two6 elements, the inference would accord closely with a view which, although he did not articulate it himself, he must have accepted as developed by others.To say that originally everything was a mixture is absurd for various reasons,