It is self-evident that if none of the individuals in a series exists by itself, then—a fortiori—the series as a whole cannot exist by itself. The totality depends on each of its parts; so when every single part is needy, contingent, and unable to subsist on its own, the collection that relies on them is even more in need and even less capable of self-existence.
An endless chain of dependents and non-existents merely multiplies non-existence; indeed, it is a regress of impossibilities. Whatever does not exist unless something else that likewise does not exist should first exist is impossible. To posit a set made up entirely of effects, with nothing among them but an effect and with no agent distinct from them, is necessarily impossible. The mere abundance of such impossible, dependent entities can never confer possibility on any one of them, let alone actual existence.
A regress in the very root of complete causation is no different from a regress in the root of causation itself. The true agent must be living, knowing, powerful, willing, and acting of Himself. Hence it is inadmissible to say: “He does not become an agent for anything until another makes Him an agent, and that other does not become an agent until yet another makes him an agent,” and so on without end. One must affirm an agent who is, in and of Himself, an agent whom no other has made so; otherwise the statement reduces to, “Nothing exists until something exists.”
Likewise, it cannot be said: “He does not act until He knows, nor does He know until another causes Him to know, and that other does not know until another causes him to know,” ad infinitum; there must be a knower by Himself. Nor may it be said: “He is not capable until another empowers Him, and that other is not capable until yet another empowers him,” endlessly; there must be one who is capable in and of Himself.
And the same holds true if someone were to assert: “He cannot be an agent until He is already an agent; He cannot be knowledgeable at all until He is knowledgeable; He cannot be capable at all until He is capable; then…”