summa-contra-gentiles

CHAPTER XXXIII 69
which has no contrary. Therefore it is impossible for
certain creatures not to exist : and consequently
it is
necessary that they exist always.
Again. A thing's endurance in being is in proportion
to its
power of being, except accidentally, as in those which
are corrupted by violence. But there are certain creatures
in which there is a power of being not for any definite time,
but for ever ;
for instance Hke heavenly bodies and intellectual
substances, because they are incorruptible through
having no contrary. It foTTows, then, that it is
competent
to them to be always. But that which begins to exist, is
not always. Therefore it is not becoming to them that they
begin to exist.
Further. Whenever a thing begins to be moved anew,
the mover, or the moved, or both, must be conditioned
otherwise now while the movement is, than before when
there was no movement : for there is a certain habitude or
relation in the mover to the thing moved, for as much as it
moves actually ;
and the new relation does not begin without
a change either in both or at least in one or other of the
extremes. Now that which is conditioned otherwise now
and heretofore, is moved. ^
Therefore, before the movement
that begins anew, there must be a previous movement either
in the movable or in the mover. It follows, in consequence,
that every movement is either eternal, or has another movement
preceding
it. Therefore movement always has been ;
and consequently movable also. Therefore there have
always been creatures : since God is utterly immovable, as
we proved in the First Book.^
Further. Every agent that engenders its like, intends to
preserve perpetual being in the species,
for it cannot be
preserved perpetually in the individual. But it is impossible
for the desire of nature to be frustrated. Therefore it
follows that the species of generable things are everlasting.
Again. If time is everlasting, movement must be everlasting,
since it is the reckoning of movement:^ and consequently
movables must be everlasting,
since movement is
1 5 Phys. i. 7.
« Ch. xiu. »
4 Phys. xi.