I claimed in an earlier post that a correct understanding of Aristotle, Metaphysics Z 3, required that we draw a distinction. I now want to explain what I believe that distinction to be, and how it figures in Aristotle's argument.
The distinction is in two ways of understanding a hypokeimenon ('substrate', 'presupposition', 'underlying thing'.) Recall Aristotle's professedly schematic account of a hypokeimenon:
That with respect to which other things are predicated but which is not itself predicated of something else.I begin by asking a question: Have you noticed how strange it is that, in Z 3, Aristotle should be looking at what isn't what we predicate of a thing? If I say, "A man is pale", how odd that I'd be interested in something which wasn't human or wasn't pale. Presumably we predicate something of something else precisely because it is that.
This reflection then leads to the articulation of two options:
Hypokeimenon 1: "that with respect to which other things are predicated but which is not predicated of something else, and which is what is predicated".(Call Hypokeimenon 1, if you wish, 'that which underlies a predication', and Hypokeimenon 2, 'that which underlies what is predicated'. This way of putting it shows how both these uses correspond to senses in which something 'underlies'.)
Hypokeimenon 2: "that with respect to which other things are predicated but which is not predicated of something else, and which is not what is predicated."
It is because Aristotle has this distinction in mind, I believe, that, at the beginning of Z 3, he distinguishes form, matter, and composite. In using Hypokeimenon 1 we can pick out either the composite substance (the bronze sphere) or the form (its sphericity); in using Hypokeimenon 2 we identify the matter of a thing. Hypokeimenon 1 is clearly the standard case, because standardly something is what is predicated of it, and this is standardly what we are interested in.
What Aristotle does in the dialectical portion of Z 3 is to show that the notion of Hypokeimenon 2, if employed just on its own, and if used as the criterion of substance, leads to the absurd conclusion that the ultimate matter of a thing--which is actually nothing--is the substance of a thing.
What I mean by 'employed just on its own' may be illustrated by a contrast. I can ask, of a bronze sphere, what serves as the Hypokeimenon 2 for its sphericity. The answer is: the bronze. In that case I give a fairly mundane answer. I am asking a question about how the bronze sphere may be regarded as having been generated or made: what was it such that it wasn't a sphere but became spherical through the imposition of the form, sphericity? And, in response, I identify what was such that the predicate 'sphere' was not true of it at first, but became true of it later. (Aristotle calls this sort of hypokeimenon the 'proximate' matter.) But note that this inquiry into the Hypokeimenon 2 presupposes some prior identification of a Hypokeimenon 1: I must first identify either this particular bronze sphere, the matter of which I wish to explain, or the form of sphericity which has been imparted to this matter, before I can identify what serves as the hypokeimenon, in the sense of 'matter', for that.
That is to say: the notion of Hypokeimenon 2, if used on its own, leads to an absurd result; if used in service of some prior notion of a Hypokeimenon 1, then it leads to a definite investigation into the composition of a thing (its proximate matter). That is why an important conclusion of Z 3 is that 'form and the composite are prior to matter' in this regard (1029a29-30); that is to say, that sense of 'hypokeimenon' which picks out the form or the composite is presupposed by any intelligible use of 'hypokeimenon' in the other sense.
We get a very important result from what I am maintaining. It follows from these considerations, I think, that Z 7-9 should be interpreted as Aristotle's investigation of the hypokeimenon in Z. Z 3 is not, as is commonly thought, his consideration of the hypokeimenon criterion: that chapter simply introduces the distinction noted above and, as it were, makes clear the proper way in which the hypokeimenon should be investigated. Z 7-9 carry out this investigation. Those chapters are not an unmotivated intrusion. (Moreover, the summary in H 1 turns out to be wholly in order. It is the case, as that summary says, that Aristotle in Z first investigates the to ti en einai and then investigates the hypokeimenon.)
Have I made my meaning clear to you? If not, post a comment, and I'll be happy to reply.