To establish the existence of the active celestial forces we argue as follows: All newly occurring events in this elemental world must have causes. Those causes are either themselves originated or eternal. If they are originated, they in turn require other causes, leading to an infinite regress—which is impossible, for an efficient cause must exist together with its effect. Were the cause of every contingent event itself another contingent event ad infinitum, all those endless causes and effects would have to exist simultaneously. Yet that is impossible, because the entire aggregate is contingent and originated, both in its totality and in each of its parts, and every contingent, originated thing needs a cause distinct from itself. Hence that aggregate—taken as a whole and in every one of its parts—would depend on something outside the totality of contingent beings, and the components of that totality can neither be necessary nor eternal. Thus all contingent beings ultimately terminate in a necessarily existent being, and the notion of an infinite regress collapses.

Once it is established that every contingent and originated thing traces back to an eternal, necessarily existent cause, we say: either everything required for that cause to be effective was present from pre-eternity, or it was not. The latter alternative encompasses the view of those who maintain that He created this particular entity at this particular moment because creating it now is more fitting than creating it at another time.