The Categories | Page 6

species. It is true that, inasmuch as primary substance is not predicable
of anything, it can never form the predicate of any proposition. But of
secondary substances, the species is predicated of the individual, the

genus both of the species and of the individual. Similarly the
differentiae are predicated of the species and of the individuals.
Moreover, the definition of the species and that of the genus are
applicable to the primary substance, and that of the genus to the species.
For all that is predicated of the predicate will be predicated also of the
subject. Similarly, the definition of the differentiae will be applicable to
the species and to the individuals. But it was stated above that the word
'univocal' 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 the
case; but that no single substance admits of varying degrees within
itself. For instance, one particular substance, 'man', cannot be more or
less man either than himself at some other time or than some other man.
One man cannot be more man than another, as that which is white may
be more or less white than some other white object, or as that which is
beautiful may be more or less beautiful than some other beautiful
object. The same quality, moreover, is said to subsist in a thing in
varying degrees at different times. A body, being white, is said to be
whiter at one time than it was before, or, being warm, is said to be
warmer or less warm than at some other time. But substance is not said
to be more or less that which it is: a man is not more truly a man at one
time than he was before, nor is anything, if it is substance, more or less
what it is. Substance, then, does not admit of variation of degree.
The most distinctive mark of substance appears to be that, while
remaining numerically one and the same, it is capable of admitting
contrary qualities. From among things other than substance, we should
find ourselves unable to bring forward any which possessed this mark.
Thus, one and the same colour cannot be white and black. Nor can the
same one action be good and bad: this law holds good with everything
that is not substance. But one and the selfsame substance, while
retaining its identity, is yet capable of admitting contrary qualities. The
same individual person is at one time white, at another black, at one
time warm, at another cold, at one time good, at another bad. This
capacity is found nowhere else, though it might be maintained that a
statement or opinion was an exception to the rule. The same statement,
it is agreed, can be both