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