the aggregate depends on each of its constituent parts: the Necessary Existent and contingent existents. The aggregate, considered as an aggregate, depends on each part just as it depends on every other part, since it exists only when all its constituent parts exist. Then, if one part is the cause of another, the aggregate depends both on the Necessary Existent as a constituent part and on the constituent part that depends on it. This does not entail that the Necessary Existent alone brings about the aggregate without an intermediary. Rather, without the other, contingent constituent part, the aggregate would not exist n. Thus, the Necessary Existent alone is not the cause of the aggregate considered as an aggregate; it is only the cause of the remaining constituent parts, while it and those remaining parts together are the cause of the aggregate.

It does follow that the Necessary Existent is itself the cause of contingent existents and, through them or together with them, is the cause of the aggregate considered as an aggregate. Nothing comparable applies to the contingent constituent parts, for no such part can be the cause of the aggregate, either by itself or through something else.

As for the first possibility, if even the necessary constituent part is not alone the cause of the aggregate, then all the more so the contingent constituent part. Moreover, the aggregate depends on all its constituent parts, so none of them can bring it about independently.

As for the second possibility, a contingent existent cannot be the cause of itself or of the causes that precede it. Furthermore, the aggregate necessarily depends on all its constituent parts, and an effect cannot be the cause of its own cause. And if it cannot be the cause of itself or of the other preceding constituent parts