Study Notes of Metaphysics Z14-16. Z14: The Platonic conception of forms was associated with the claim that universals are substances.
(1) If “animal” is supposed the same in horse and in man, (a) how can it be the same in things that exist apart? (b) If it shares in “two-footed” and in “many-footed,” it will have contrary attributes; if it does not, in what sense can it be two-footed?
(2) If “animal” is different in each species, (a) there will be practically an infinity of things whose substance is “animal.” (b) Each of several things will be “animal itself.” (c) From what will the “animal” in each species be derived?
(3) These and even greater difficulties arise if we consider the relation of Forms to sensible things.
Z15 This chapter argues that no particular (individuals + Forms) is definable.
(1) Particular sensible substances are not subjects of definition or of demonstration, because the have matter capable of being and of not being.
(2) Forms cannot be defined, too, for (a) they are said to be a separate particular. If Forms can be defined, then (i) they will belong to both elements in the definition, e.g. “two-footed animal” belongs to “animal” and to “the two-footed,” and (ii) the elements are prior to the whole and therefore are not removed when the whole is removed.
(b) If the elements of Forms are Forms, the elements, e.g. “animal” and “two-footed,” will be predicable of many subjects.
Z16 A substance must be one, yet one cannot be the substance of a thing.
(1) Most so-called substances are potentialities, i.e. the parts of animals and elements, because they are not unities but simply aggregates till they are fused into one. They exist only potentially when they are united by nature.
(2) Neither unity nor being can be the substance of things, since “unity is predicated in the same way as being,” and the substance of what is one is one, and things whose substance is one are one. We still have to ask what the principle is.
Unity and being are more substantial than “principle” or “element” or “cause,” but they are not substances, because (a) they are common, while substance belongs only to itself and to that which has it, and (b) one thing cannot be in many places at once, while what is common can. Hence no universal exists separately from particulars.
(3) Diagnosis of the basic error of those who believe in the forms (the word used is eidos rather then idea): the one over many is a Form.
(4) Therefore no universal is a substance and no substance is composed of substances.
