On Longevity And Shortness Of Life
place where what is corruptible becomes incorruptible, as fire does in
the upper regions where it meets with no opposite. Opposites destroy
each other, and hence accidentally, by their destruction, whatsoever
is attributed to them is destroyed. But no opposite in a real
substance is accidentally destroyed, because real substance is not
predicated of any subject. Hence a thing which has no opposite, or
which is situated where it has no opposite, cannot be destroyed. For
what will that be which can destroy it, if destruction comes only
through contraries, but no contrary to it exists either absolutely
or in the particular place where it is? But perhaps this is in one
sense true, in another sense not true, for it is impossible that
anything containing matter should not have in any sense an opposite.
Heat and straightness can be present in every part of a thing, but
it is impossible that the thing should be nothing but hot or white
or straight; for, if that were so, attributes would have an
independent existence. Hence if, in all cases, whenever the active and
the passive exist together, the one acts and the other is acted on, it
is impossible that no change should occur. Further, this is so if a
waste product is an opposite, and waste must always be produced; for
opposition is always the source of change, and refuse is what
remains of the previous opposite. But, after expelling everything of a
nature actually opposed, would an object in this case also be
imperishable? No, it would be destroyed by the environment.
If then that is so, what we have said sufficiently accounts for
the change; but, if not, we must assume that something of actually
opposite character is in the changing object, and refuse is produced.
Hence accidentally a lesser flame is consumed by a greater one,
for the nutriment, to wit the smoke, which the former takes a long
period to expend, is used up by the big flame quickly.
Hence [too] all things are at all times in a state of transition and
are coming into being and passing away. The environment acts on them
either favourably or antagonistically, and, owing to this, things that