Substance, in the truest and primary and most definite sense of
the word, is that which is neither predicable of a subject nor
present in a subject; for instance, the individual man or horse.
But in a secondary sense those things are called substances
within which, as species, the primary substances are included;
also those which, as genera, include the species. For instance,
the individual man is included in the species 'man', and the
genus to which the species belongs is 'animal'; these,
therefore-that is to say, the species 'man' and the genus
'animal,-are termed secondary substances.
It is plain from what has been said that both the name and the
definition of the predicate must be predicable of the subject.
For instance, 'man' is predicted of the individual man. Now in
this case the name of the species man' is applied to the
individual, for we use the term 'man' in describing the
individual; and the definition of 'man' will also be predicated
of the individual man, for the individual man is both man and
animal. Thus, both the name and the definition of the species are
predicable of the individual.
With regard, on the other hand, to those things which are present
in a subject, it is generally the case that neither their name
nor their definition is predicable of that in which they are
present. Though, however, the definition is never predicable,
there is nothing in certain cases to prevent the name being used.
For instance, 'white' being present in a body is predicated of
that in which it is present, for a body is called white: the
definition, however, of the colour white' is never predicable of
Everything except primary substances is either predicable of a
primary substance or present in a primary substance. This becomes
evident by reference to particular instances which occur.
'Animal' is predicated of the species 'man', therefore of the
individual man, for if there were no individual man of whom it
could be predicated, it could not be predicated of the species
'man' at all. Again, colour is present in body, therefore in
individual bodies, for if there were no individual body in which
it was present, it could not be present in body at all. Thus
everything except primary substances is either predicated of
primary substances, or is present in them, and if these last did
not exist, it would be impossible for anything else to exist.