its cause, it becomes necessary. If no condition is attached to it—neither the presence of a cause nor its absence—there remains for it, in itself, the third alternative: possibility. Thus, considered in itself, it is something whose existence is neither necessary nor impossible. Every existent, therefore, is either necessary in itself or possible in itself.

Indication: Whatever is intrinsically possible does not come to exist by virtue of itself, for, insofar as it is possible, its existence by virtue of itself has no priority over its nonexistence. If either acquires priority, this is due to the presence or absence of something. Thus, the existence of everything whose existence is possible derives from something other than itself.”

Then he said:

“Reminder: Either this proceeds in an infinite regress, in which case every member of the chain is possible in itself. The aggregate depends on these members and is therefore likewise not necessary in itself, but becomes necessary through something else. Let us return to this for further clarification.