God is Independent, α. in Existence, whence He is said Necessarily to Exist. Which Necessary Existence of God we prove, 1. a priori, a. From the Infinite Perfection of God. For, what exists as infinitely Perfect exists necessarily; because the Necessity of existence is a simple and absolute Perfection. That is, what thing exists in such a way that it is not able not to exist is Necessary with respect to Existence. To this is opposed a Contingent thing; which exists in such a way that it is able not to exist. Now, something is More Perfect than nothing, to be than not to be; since according to the Metaphysicians each thing has Goodness and Perfect only to the extent that it has Being. But in like manner not to be able to be is also More Perfect than to be able not to be; not to be able to become nothing than to be able to become Nothing, of which, as there are no affections, so neither are there any Perfections: for what is further distant from the imperfect and is the more adverse to it, the More Perfect that is also to be considered. b. From the Independence of God generally asserted in § 20. For every Contingency involves Dependence. For a Contingent thing, by this very thing, that it is able not to be, of itself is not bound to exist; and so it requires a Cause outside of itself, which makes it to be rather than not to be; or by the influx of which a thing of itself indifferent unto either may be determined to exist rather than not to exist. Which dependence upon the influx of a Cause, since divine Independence altogether rejects it, the same likewise rejects all Contingency involving dependence of this sort: consequently it is manifest that it includes the opposite Necessity of existence. To which, 2. a posteriori an argument is able to be added from the very Contingency of created things. For a great many contingent things are everywhere obvious to us, which of and by themselves are not able to exist. And so, if you inquired into the Cause by which those exist, and identify this Cause in turn as contingent; then that also will in turn have its own cause. If this Cause is again recognized as contingent, the same question will return: since this is not able to be repeated unto infinity (because a series of subordinate Causes is necessarily finite); it is necessary that that Being in which we subsist as in the first cause of contingent things is Necessary in Existing.
Then, β. in Essence, which from the thing said in § 20 is evident of itself. For, if God is Independent and Sufficient for Himself, by what reason is He better to be asserted as such, than by reason of the divine Essence? especially since in divine things there is the closest tie between Essence and Existence, which we just now demonstrated that God possesses by reason of independence.