Chapter 1
There are several senses in which a thing may be said to 'be', as we pointed out previously in our book on the various senses of words;[1] for in one sense the 'being' meant is 'what a thing is' or the individual thing, and in another sense it means that a thing is of a certain quality or quantity or has some such predicate asserted of it. While 'being' has all these senses, obviously that which 'is' primarily is the 'what', which indicates the substance of the thing. For when we say of what quality a thing is, we say that it is good or beautiful,[2] but not that it is three cubits long or that it is a man; but when we say what it is, we do not say 'white' or 'hot' or 'three cubits long', but 'man' or 'God'. And all other things are said to be because they are, some of them, quantities of that which is in this primary sense, others qualities of it, others affections of it, and others some other determination of it. And so one might raise the question whether walking and being healthy and sitting are, each of them, existent or non-existent, and similarly in any other case of this sort; for none of them is either self-subsistent or capable of being separated from substance, but rather, if anything, it is that which walks or is seated or is healthy that is an existent thing. Now these are seen to be more real because there is something definite which underlies them; and this is the substance or individual, which is implied in such a predicate; for 'good' or 'sitting' apart from that which sits or is good has no meaning. Clearly then it is in virtue of this category that each of the others is. Therefore that which is primarily and is simply (not 'is something') must be substance.
Now there are several senses in which a thing is said to be first; but substance is first in every sense — (1) in formula,
