Explanation:
Every aggregate whose individual members are all caused requires a cause external to its members. For either it requires a cause at all, in which case it is necessary and uncaused—but how can this be, when it becomes necessary only through its members? Or it requires a cause consisting of all its members, in which case it is caused by itself, since that aggregate and the whole are one and the same. As for “all” in the sense of each individual member, the aggregate does not become necessary through any one of them. Or it requires a cause consisting of some of its members, some having a greater claim to this role than others if each of them is caused, since the cause of such a member has a greater claim to that role. Or it requires a cause external to all its members; this is the second alternative.

Indication:
Every cause of an aggregate that is distinct from each of its members is a cause first of the members, and then of the aggregate. Otherwise, suppose that the members have no need of it. Once the aggregate is complete through its members, it would have no need of that cause. Indeed, something may be a cause of some