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was applied to those things which had both name and definition in

common. It is, therefore, established that in every proposition, of

which either substance or a differentia forms the predicate, these are

predicated univocally.

All substance appears to signify that which is individual. In the

case of primary substance this is indisputably true, for the thing

is a unit. In the case of secondary substances, when we speak, for

instance, of 'man' or 'animal', our form of speech gives the

impression that we are here also indicating that which is

individual, but the impression is not strictly true; for a secondary

substance is not an individual, but a class with a certain

qualification; for it is not one and single as a primary substance is;

the words 'man', 'animal', are predicable of more than one subject.

Yet species and genus do not merely indicate quality, like the

term 'white'; 'white' indicates quality and nothing further, but

species and genus determine the quality with reference to a substance:

they signify substance qualitatively differentiated. The determinate

qualification covers a larger field in the case of the genus that in

that of the species: he who uses the word 'animal' is herein using a

word of wider extension than he who uses the word 'man'.

Another mark of substance is that it has no contrary. What could

be the contrary of any primary substance, such as the individual man

or animal? It has none. Nor can the species or the genus have a

contrary. Yet this characteristic is not peculiar to substance, but is

true of many other things, such as quantity. There is nothing that

forms the contrary of 'two cubits long' or of 'three cubits long',

or of 'ten', or of any such term. A man may contend that 'much' is the

contrary of 'little', or 'great' of 'small', but of definite

quantitative terms no contrary exists.

Substance, again, does not appear to admit of variation of degree. I

do not mean by this that one substance cannot be more or less truly

substance than another, for it has already been stated' that this is