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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