; therefore, either nothing exists, or else a being
absolutely infinite necessarily exists also. Now we exist either
in ourselves, or in something else which necessarily exists (see
Axiom. i. and Prop. vii.). Therefore a being absolutely
infinite--in other words, God (Def. vi.)--necessarily exists.
Q.E.D.

Note.--In this last proof, I have purposely shown God's
existence a posteriori, so that the proof might be more easily
followed, not because, from the same premises, God's existence
does not follow a priori. For, as the potentiality of existence
is a power, it follows that, in proportion as reality increases
in the nature of a thing, so also will it increase its strength
for existence. Therefore a being absolutely infinite, such as
God, has from himself an absolutely infinite power of existence,
and hence he does absolutely exist. Perhaps there will be many
who will be unable to see the force of this proof, inasmuch as
they are accustomed only to consider those things which flow from
external causes. Of such things, they see that those which
quickly come to pass--that is, quickly come into existence--quickly
also disappear; whereas they regard as more difficult of
accomplishment--that is, not so easily brought into
existence--those things which they conceive as more complicated.

However, to do away with this misconception, I need not here
show the measure of truth in the proverb, "What comes quickly,
goes quickly," nor discuss whether, from the point of view of
universal nature, all things are equally easy, or otherwise: I
need only remark that I am not here speaking of things, which
come to pass through causes external to themselves, but only of
substances which (by Prop. vi.) cannot be produced by any
external cause. Things which are produced by external causes,
whether they consist of many parts or few, owe whatsoever
perfection or reality they possess solely to the efficacy of
their external cause; and therefore their existence arises
solely from the perfection of their external cause, not from
their own. Contrariwise, whatsoever perfection is possessed by
substance is due to no external cause; wherefore the existence
of substance must arise solely from its own nature, which is
nothing else but its essence. Thus, the perfection of a thing
does not annul its existence, but, on the contrary, asserts it.
Imperfection, on the other hand, does annul it; therefore we
cannot be more certain of the existen