He said:

“In that case, the assertion that what exists is divided into that which has a cause and that which has no cause requires proof.”

He said:

“Then that which has a cause is divided into the possible and the necessary. The necessary is that which cannot cease to exist, but is always necessarily existent by virtue of its cause. The genuinely possible is that which could either exist or not exist, namely, that which was nonexistent.

“Thus, what is genuinely possible can only have come into existence. This entails the existence of something necessarily existent—that is, something necessary—but does not entail that it has no cause, except on the basis of a separate proof.”

He said:

“If we take ‘possible’ to mean that which has a cause, the proposition amounts to saying that whatever has a cause has a cause. It is then possible to posit an endless series of possible things. The sequence therefore does not end in an existent without a cause—what they call the Necessary Existent—unless ‘possible’, which he sets in opposition to that which has no cause, is understood to mean the genuinely possible. For it is precisely these possible things whose causes cannot extend endlessly.

“But if by ‘possible’ he means those necessary things that have a cause, it has not yet been shown that this is impossible in the way it has been shown to be impossible for genuinely possible existents. Nor has it yet been shown that there is anything necessary here that requires a cause, such that it could be said that the sequence must ultimately end