And a thing that comes into existence was nonexistent at one time and existent at another. It therefore cannot be impossible, because what is impossible cannot exist; nor can it be necessary in itself, because what is necessary in itself cannot cease to exist. It is thus established that it is contingent, that some existing things are contingent in themselves, and that not all existing things are contingent. Hence, among them there must be something that is not contingent. An existing being that is not contingent is necessary in itself, for an existing being either exists through itself, in which case it is necessary, or through something else, in which case it is contingent. It cannot be impossible, because what is impossible cannot exist; thus, nothing impossible can be found among existing things.
It is therefore clear that existing things include both necessary and contingent beings, but nothing impossible.
Alternatively, you may say: a being either admits nonexistence in itself, in which case it is contingent, or does not admit nonexistence, in which case it is necessary in itself. Or you may say: it either depends upon something else, in which case it is contingent, or does not, in which case it is necessary.
Since existing things are either necessary or contingent, and neither all contingent nor all necessary, it follows that they include both necessary and contingent beings.
[The Second Argument]
One may say that anything contingent in itself exists only through something that makes its existence necessary. For if that which makes its existence necessary is not present, it remains contingent, admitting either existence or nonexistence, and therefore does not exist.
That which makes its existence necessary cannot itself be contingent, because nothing contingent can make anything necessary, since it depends upon something else. Thus, whatever depends upon a contingent being depends both upon it and upon that which made the contingent being’s existence necessary. Since a contingent being alone cannot make anything necessary, we know that a contingent being depends upon something necessary in itself.