Hortatory Address to the Greeks

And that these very wonderful sages of yours do not even agree in other respects, can be easily learned from this. For while Plato says that there are three first principles of all things, God, and matter, and form,— God, the maker of all; and matter, which is the subject of the first production of all that is produced, and affords to God opportunity for His workmanship; and form, which is the type of each of the things produced—Aristotle makes no mention at all of form as a first principle, but says that there are two, God and matter.

And again, while Plato says that the highest God and the ideas exist in the first place of the highest heavens, and in fixed sphere, Aristotle says that, next to the most high God, there are, not ideas, but certain gods, who can be perceived by the mind. Thus, then, do they differ concerning things heavenly. So that one can see that they not only are unable to understand our earthly matters, but also, being at variance among themselves regarding these things, they will appear unworthy of credit when they treat of things heavenly.

And that even their doctrine regarding the human soul as it now is does not harmonize, is manifest from what has been said by each of them concerning it. For Plato says that it is of three parts, having the faculty of reason, of affection, and of appetite. But Aristotle says that the soul is not so comprehensive as to include also corruptible parts, but only reason. And Plato loudly maintains that “the whole soul is immortal.” But Aristotle, naming it “the actuality,” would have it to be mortal, not immortal. And the former says it is always in motion; but Aristotle says that it is immoveable, since it must itself precede all motion.