but if they had a cause distinct from them, both would be contingent and dependent (1) upon something necessary in itself, and the same argument would apply to it as applies to them.

However, if both were necessary in themselves, it would be impossible for the existence of either one—or of any of its necessary concomitants—to be through the other. Each would thereby be a cause, or part of a cause, of the other, since each would be complete only through the other. Yet neither could be a cause or part of a cause unless it existed, for that which does not exist cannot affect anything else or act as its agent. Thus (2) this one cannot affect that one until this one exists, (* nor can that one affect this one until that one exists (3) *) (4). It follows that this one cannot exist until that one exists (5), and that one cannot exist until this one exists. Nor can this one exist until its own effect exists, which would make this one the agent of its own agent. Likewise, that one cannot exist until the agent of [that one] (6) exists, which would make that one the agent of its own agent.

It is well known that, whatever terms are used to express this meaning, it is impossible for a thing to be its own cause, part of its own cause, or a condition of its own cause. Accordingly, it cannot be the agent that produces itself, part of such an agent, a condition of the agent that produces it, or the completion of that agent; nor can it exercise causal influence upon itself or complete that which exercises causal influence upon it. Hence, a created being