existence from its true nature. It follows that the cause of a thing’s existence at one time must be like, and of the same kind as, the cause of another thing’s existence at a different time.

Accordingly, one cause must precede the other because of a second cause. The same reasoning applied to the first applies to the second and to its necessary dependence upon a third—if its precedence is due to a cause.

The same applies to the cause of coming later. This entails an infinite succession of things coming into being, which is impossible.

If the opponent acknowledges that a thing whose existence precedes that of another like it does so because of a cause brought about by an agent, he thereby concedes that the act depends upon the agent. The effect would then stand on the same footing as the cause, which establishes what we intended.

If, however, he denies that the cause necessitating the existence of what comes into being through it depends upon the agent, he is confronted by the argument we have just addressed to him: there is no more reason for some substances to bear that which necessitates their existence at one time after another than for it to be present in other substances like them.”

He said:

“We shall explain later that the enumerated substances are neither entities, nor individual realities, nor substances before accidents exist, and that they come into existence only together with those accidents.

We did not introduce this topic earlier in this proof simply because we have no need