Third Article: Whether God Exists?
We proceed thus to the Third Article:—
Objection 1. It seems that God does not exist; because if one of two contraries be infinite,
the other would be altogether destroyed. But the word ‘God’ means that He is infinite
goodness. If, therefore, God existed, there would be no evil discoverable; but there
is evil in the world. Therefore God does not exist.
Obj. 2. Further, it is superfluous to suppose that what can be accounted for by a few
principles has been produced by many. But it seems that everything we see in the world
can be accounted for by other principles, supposing God did not exist. For all natural
things can be reduced to one principle, which is nature; and all voluntary things
can be reduced to one principle, which is human reason, or will. Therefore there is
no need to suppose God’s existence. On the contrary, It is said in the person of God: I am Who am (Exod. iii. 14).
I answer that, The existence of God can be proved in five ways.
The first and more manifest way is the argument from motion. It is certain, and evident
to our senses, that in the world some things are in motion. Now whatever is in motion
is put in motion by another, for nothing can be in motion except it is in potentiality
to that towards which it is in motion; whereas a thing moves inasmuch as it is in
act. For motion is nothing else than the reduction of something from potentiality
to actuality. But nothing can be reduced from potentiality to actuality, except by
something in a state of actuality. Thus that which is actually hot, as fire, makes
wood, which is potentially hot, to be actually hot, and thereby moves and changes
it. Now it is not possible that the same thing should be at once in actuality and
potentiality in the same respect, but only in different respects. For what is actually
hot cannot simultaneously be potentially hot; but it is simultaneously potentially
cold. It is therefore impossible that in the same respect and in the same way a thing
should be both mover and moved, i.e., that it should move itself. Therefore, whatever
is in motion must be put in motion by another. If that by which it is put in motion
be itself put in motion, then this also must needs be put in motion by another, and
that by another again. But this cannot go on to infinity, because then there would
be no first mover, and, consequently, no other mover; seeing that subsequent movers
move only inasmuch as they are put in motion by the first mover; as the staff moves
only because it is put in motion by the hand. Therefore it is necessary to arrive
at a first mover, put in motion by no other; and this everyone understands to be God.
The second way is from the nature of the efficient cause. In the world of sense we
find there is an order of efficient causes. There is no case known (neither is it,
indeed, possible) in which a thing is found to be the efficient cause of itself; for
so it would be prior to itself, which is impossible. Now in efficient causes it is
not possible to go on to infinity, because in all efficient causes following in order,
the first is the cause of the intermediate cause, and the intermediate is the cause
of the ultimate cause, whether the intermediate cause be several, or one only. Now
to take away the cause is to take away the effect. Therefore, if there be no first
cause among efficient causes, there will be no ultimate, nor any intermediate cause.
But if in efficient causes it is possible to go on to infinity, there will be no first
efficient cause, neither will there be an ultimate effect, nor any intermediate efficient
causes; all of which is plainly false. Therefore it is necessary to admit a first
efficient cause, to which everyone gives the name of God.
The third way is taken from possibility and necessity, and runs thus. We find in nature
things that are possible to be and not to be, since they are found to be generated,
and to corrupt, and consequently, they are possible to be and not to be. But it is
impossible for these always to exist, for that which is possible not to be at some
time is not. Therefore, if everything is possible not to be, then at one time there
could have been nothing in existence. Now if this were true, even now there would
be nothing in existence, because that which does not exist only begins to exist by
something already existing. Therefore, if at one time nothing was in existence, it
would have been impossible for anything to have begun to exist; and thus even now
nothing would be in existence—which is absurd. Therefore, not all beings are merely
possible, but there must exist something the existence of which is necessary. But
every necessary thing either has its necessity caused by another, or not. Now it is
impossible to go on to infinity in necessary things which have their necessity caused
by another, as has been already proved in regard to efficient causes. Therefore we
cannot but postulate the existence of some being having of itself its own necessity,
and not receiving it from another, but rather causing in others their necessity. This
all men speak of as God.
The fourth way is taken from the gradation to be found in things. Among beings there
are some more and some less good, true, noble, and the like. But ‘more’ and ‘less’
are predicated of different things, according as they resemble in their different
ways something which is the maximum, as a thing is said to be hotter according as
it more nearly resembles that which is hottest; so that there is something which is
truest, something best, something noblest, and, consequently, something which is uttermost
being; for those things that are greatest in truth are greatest in being, as it is
written in Metaph. ii. Now the maximum in any genus is the cause of all in that genus; as fire, which
is the maximum of heat, is the cause of all hot things. Therefore there must also
be something which is to all beings the cause of their being, goodness, and every
other perfection; and this we call God.
The fifth way is taken from the governance of the world. We see that things which
lack intelligence, such as natural bodies, act for an end, and this is evident from
their acting always, or nearly always, in the same way, so as to obtain the best result.
Hence it is plain that not fortuitously, but designedly, do they achieve their end.
Now whatever lacks intelligence cannot move towards an end, unless it be directed
by some being endowed with knowledge and intelligence; as the arrow is shot to its
mark by the archer. Therefore some intelligent being exists by whom all natural things
are directed to their end; and this being we call God.
Reply Obj. 1. As Augustine says (Enchir. xi.): Since God is the highest good, He would not allow any evil to exist in His works,
unless His omnipotence and goodness were such as to bring good even out of evil. This is part of the infinite goodness of God, that He should allow evil to exist,
and out of it produce good.
Reply Obj. 2. Since nature works for a determinate end under the direction of a higher agent,
whatever is done by nature must needs be traced back to God, as to its first cause.
So also whatever is done voluntarily must also be traced back to some higher cause
other than human reason or will, since these can change and fail; for all things that
are changeable and capable of defect must be traced back to an immovable and self-necessary
first principle, as was shown in the body of the Article.