THERE are several senses in which a thing may be said to ‘be’
In one sense the ‘being’ meant is ‘what a thing is’ or a ’this’
In another sense it means a quality or quantity or one of the other things that are predicated as these are.
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 bad, 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 ‘a man’ or ‘a ‘god’.
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.
So one might even raise the question whether the words ’to walk’, ’to be healthy’, ’to sit’ imply that each of these things is 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 sits or is healthy that is an existent thing.
Now these are seen to be more real because there is something definite which underlies them (i.e. the substance or individual), which is implied in such a predicate; for we never use the word ‘good’ or ‘sitting’ without implying this. Clearly then it is in virtue of this category that each of the others also is. Therefore that which is primarily, i.e. not in a qualified sense but without qualification, must be substance.
There are several senses in which a thing is said to be first; yet substance is first in every sense-
- in definition,
- in order of knowledge,
- in time.
For (3) of the other categories none can exist independently, but only substance. And (1) in definition also this is first; for in the definition of each term the definition of its substance must be present. And (2) we think we know each thing most fully, when we know what it is, e.g. what man is or what fire is, rather than when we know its quality, its quantity, or its place; since we know each of these predicates also, only when we know what the quantity or the quality is.
What is being? What is substance?
For it is this that some assert to be one, others more than one, and that some assert to be limited in number, others unlimited. And so we also must consider chiefly and primarily and almost exclusively what that is which is in this sense.
Substance is thought to belong most obviously to bodies.
The following are substances:
- animals and plants and their parts
- natural bodies such as fire and water and earth and everything of the sort
- all things that are either parts of these or composed of these e.g. the physical universe and its parts, stars and moon and sun.
Are these alone substances?
Some think the limits of body, i.e. surface, line, point, and unit, are substances, and more so than body or the solid.
Some do not think there is anything substantial besides sensible things, but others think there are eternal substances which are more in number and more real;
e.g. Plato posited two kinds of substance-the Forms and objects of mathematics-as well as a third kind, viz. the substance of sensible bodies.
Speusippus made still more kinds of substance, beginning with the One, and assuming principles for each kind of substance, one for numbers, another for spatial magnitudes, and then another for the soul; and by going on in this way he multiplies the kinds of substance.
Some say Forms and numbers have the same nature, and the other things come after them-lines and planes-until we come to the substance of the material universe and to sensible bodies.
Regarding these matters, then, we must inquire which of the common statements are right and which are not right, and what substances there are, and whether there are or are not any besides sensible substances, and how sensible substances exist, and whether there is a substance capable of separate existence (and if so why and how) or no such substance, apart from sensible substances; and we must first sketch the nature of substance.