summa-contra-gentiles

CHAPTER XLI 91
among things thus ordered, be on account of a diversity of
agents without order.
Moreover. Things that have a cause of their distinction
cannot be the first cause of the distinction of things. Now,
if we take several co-ordinate agents, they must needs have
a cause of their distinction :
because they have a cause of
their being, since all beings are from one first being, as
was shown above ;^ and the cause of a thing's being is the
same as the cause of its distinction from others, as we have
proved.^ Therefore diversity of agents cannot be the first
cause of distinction among things.
Again.
If the diversity of things comes of the diversity
or contrariety of various agents, this would seem especially
to apply, as many maintain, to the contrariety of good and
evil, so that all
good things proceed from a good principle,
and evil things from an evil principle : for good and evil
are in every genus. But there cannot be one first principle
of all evil things. For, since those things that are through
another, are reduced to those that are of themselves, it
would follow that the first active cause of evils is evil of
itself. Now a thing
is said to be such of itself, if it is such
by its essence. Therefore its essence will not be good. But
this is impossible. For everything that is, must of necessity
be good in so far as it is a being ; because everything loves
its
being and desires it to be preserved ; a sign of which is
that everything resists its own corruption and good
is ivhat
;
all desire.^ Therefore distinction among things cannot
proceed from two contrary principles, the one good, and
the other evil.
Further. Every agent acts in as much as it is actual ;
and in as much as it is in act, everything is perfect : and
everything that is perfect, as such, is said to be good.
Therefore every agent, as such, is good. Wherefore if a
thing is essentially evil, it cannot be an agent. But if it is
the first principle of evils, it must be essentially evil, as we
have proved. Therefore it is
impossible that the distinction
among things proceed from two principles, good and evil.
1 Ch. XV.
« Ch. xl.
» I Ethic, i. i.