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