Book 7
5
For if the Ideal Good is to be different from the essence of good, and the Ideal Animal and Being from the essence of animal and being, there will be other substances and entities and Ideas besides the ones which they describe; and prior to them, if essence is substance. And if they are separate from each other, there will be no knowledge of the Ideas, and the essences will not exist
6
(by being separate I mean if neither the essence of good is present in the Ideal Good, nor being good in the essence of good); for it is when we know the essence of it that we have knowledge of a thing. And it is the same with other essences as with the essence of good; so that if the essence of good is not good, neither will the essence of being be, nor the essence of one be one.
7
Either all essences exist alike, or none of them; and so if not even the essence of being is, neither will any other essence exist. Again that to which essentially good does not apply cannot be good. Hence the good must be one with the essence of good, the beautiful with the essence of beauty, and so with all terms which are not dependent upon something else, but self-subsistent and primary.The example of the Ideas as per se terms is used by Aristotle to show incidentally the fallacy of the Ideal theory: there can be no self-subsistent entity apart from the essence.
