The Categories | Page 7

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.
Part 6

Quantity is either discrete or continuous. Moreover, some quantities are
such that each part of the whole has a relative position to the other parts:
others have within them no such relation of part to part.
Instances of discrete quantities are number and speech; of continuous,
lines, surfaces, solids, and, besides these, time and place.
In the case of the parts of a number, there is no common boundary at
which they join. For example: two fives make ten, but the two fives
have no common boundary, but are separate; the parts three and seven
also do not join at any boundary. Nor, to generalize, would it ever be
possible in the case of number that there should be a common boundary
among the parts; they are always separate. Number, therefore, is a
discrete quantity.
The same is true of speech. That speech is a quantity is evident: for it is
measured in long and short syllables. I mean here that speech which is
vocal. Moreover, it is a discrete quantity for its parts have no common
boundary. There is no common boundary at which the syllables join,
but each is separate and distinct from the rest.
A line, on the other hand, is a continuous quantity, for it is possible to
find a common boundary at which its parts join. In the case of the line,
this common boundary is the point; in the case of the plane, it is the
line: for the parts of the plane have also a common boundary. Similarly
you can find a common boundary in the case of the parts of a solid,
namely either a line or a plane.
Space and time also belong to this class of quantities. Time, past,
present, and future, forms a continuous whole. Space, likewise, is a
continuous quantity; for the parts of a solid occupy a certain space, and
these have a common boundary; it follows that the parts of space also,
which are occupied by the parts of the solid, have the same common
boundary as the parts of the solid. Thus,