The Categories

Part 5

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 predicated 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 the body.

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.

Of secondary substances, the species is more truly substance than the
genus, being more nearly related to primary substance. For if any one
should render an account of what a primary substance is, he would
render a more instructive account, and one more proper to the subject,
by stating the species than by stating the genus. Thus, he would give a
more instructive account of an individual man by stating that he was
man than by stating that he was 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 everything
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 substance 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 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 true and false. For if the statement ‘he is
sitting’ is true, yet, when the person in question has risen, the same
statement will be false. The same applies to opinions. For if any one
thinks truly that a person is sitting, yet, when that person has risen,
this same opinion, if still held, will be false. Yet although this
exception may be allowed, there is, nevertheless, a difference in the
manner in which the thing takes place. It is by themselves changing
that substances admit contrary qualities. It is thus that that which
was hot becomes cold, for it has entered into a different state.
Similarly that which was white becomes black, and that which was bad
good, by a process of change; and in the same way in all other cases it
is by changing that substances are capable of admitting contrary
qualities. But statements and opinions themselves remain unaltered in
all respects: it is by the alteration in the facts of the case that the
contrary quality comes to be theirs. The statement ‘he is sitting’
remains unaltered, but it is at one time true, at another false,
according to circumstances. What has been said of statements applies
also to opinions. Thus, in respect of the manner in which the thing
takes place, it is the peculiar mark of substance that it should be
capable of admitting contrary qualities; for it is by itself changing
that it does so.

If, then, a man should make this exception and contend that statements
and opinions are capable of admitting contrary qualities, his
contention is unsound. For statements and opinions are said to have
this capacity, not because they themselves undergo modification, but
because this modification occurs in the case of something else. The
truth or falsity of a statement depends on facts, and not on any power
on the part of the statement itself of admitting contrary qualities. In
short, there is nothing which can alter the nature of statements and
opinions. As, then, no change takes place in themselves, these cannot
be said to be capable of admitting contrary qualities.

But it is by reason of the modification which takes place within the
substance itself that a substance is said to be capable of admitting
contrary qualities; for a substance admits within itself either disease
or health, whiteness or blackness. It is in this sense that it is said
to be capable of admitting contrary qualities.

To sum up, it is a distinctive mark of substance, that, while remaining
numerically one and the same, it is capable of admitting contrary
qualities, the modification taking place through a change in the
substance itself.

Let these remarks suffice on the subject of substance.