The Categories | Page 5

animal, for the former description is
peculiar to the individual in a greater degree, while the latter is too
general. Again, the man who gives an account of the nature of an

individual tree will give a more instructive account by mentioning the
species 'tree' than by mentioning the genus 'plant'.
Moreover, primary substances are most properly called substances in
virtue of the fact that they are the entities which underlie every. else,
and that everything else is either predicated of them or present in them.
Now the same relation which subsists between primary substance and
everything else subsists also between the species and the genus: for the
species is to the genus as subject is to predicate, since the genus is
predicated of the species, whereas the species cannot be predicated of
the genus. Thus we have a second ground for asserting that the species
is more truly substance than the genus.
Of species themselves, except in the case of such as are genera, no one
is more truly substance than another. We should not give a more
appropriate account of the individual man by stating the species to
which he belonged, than we should of an individual horse by adopting
the same method of definition. In the same way, of primary substances,
no one is more truly substance than another; an individual man is not
more truly substance than an individual ox.
It is, then, with good reason that of all that remains, when we exclude
primary substances, we concede to species and genera alone the name
'secondary substance', for these alone of all the predicates convey a
knowledge of primary substance. For it is by stating the species or the
genus that we appropriately define any individual man; and we shall
make our definition more exact by stating the former than by stating the
latter. All other things that we state, such as that he is white, that he
runs, and so on, are irrelevant to the definition. Thus it is just that these
alone, apart from primary substances, should be called substances.
Further, primary substances are most properly so called, because they
underlie and are the subjects of everything else. Now the same relation
that subsists between primary substance and everything else subsists
also between the species and the genus to which the primary substance
belongs, on the one hand, and every attribute which is not included
within these, on the other. For these are the subjects of all such. If we
call an individual man 'skilled in grammar', the predicate is applicable

also to the species and to the genus to which he belongs. This law holds
good in all cases.
It is a common characteristic of all sub. stance that it is never present in
a subject. For primary substance is neither present in a subject nor
predicated of a subject; while, with regard to secondary substances, it is
clear from the following arguments (apart from others) that they are not
present in a subject. For 'man' is predicated of the individual man, but is
not present in any subject: for manhood is not present in the individual
man. In the same way, 'animal' is also predicated of the individual man,
but is not present in him. Again, when a thing is present in a subject,
though the name may quite well be applied to that in which it is present,
the definition cannot be applied. Yet of secondary substances, not only
the name, but also the definition, applies to the subject: we should use
both the definition of the species and that of the genus with reference to
the individual man. Thus substance cannot be present in a subject.
Yet this is not peculiar to substance, for it is also the case that
differentiae cannot be present in subjects. The characteristics
'terrestrial' and 'two-footed' are predicated of the species 'man', but not
present in it. For they are not in man. Moreover, the definition of the
differentia may be predicated of that of which the differentia itself is
predicated. For instance, if the characteristic 'terrestrial' is predicated of
the species 'man', the definition also of that characteristic may be used
to form the predicate of the species 'man': for 'man' is terrestrial.
The fact that the parts of substances appear to be present in the whole,
as in a subject, should not make us apprehensive lest we should have to
admit that such parts are not substances: for in explaining the phrase
'being present in a subject', we stated' that we meant 'otherwise than as
parts in a whole'.
It is the mark of substances and of differentiae that, in all propositions
of which they form the predicate, they are predicated univocally. For all
such propositions have for their subject either the individual or the