The underlying principle in all this is that only what has ceased to exist has entered into existence, and whatever has ceased to exist must have begun to exist, since only what began to exist can cease to exist. It would follow that an infinity extending into the past had entered into existence only if its entry into existence—I mean, that of the infinity—had been simultaneous. But when things enter into existence one individual after another in one and the same subject—as though you had said, in the revolving body—and there is no first, it does not follow that those which have entered into existence must be bounded or finite. For the finite is that to which something can be added, and any totality we suppose to be finite may contain a totality preceded by another totality.

This is the definition of the kind of infinity whose existence is possible: there is always something beyond it.

They should be asked: Just as the existence of the Creator, glorified and exalted be He, is conceived as infinite into the past, and just as His existence is conceived as infinite into the future—this is what we mean when we say that He has always existed and will always exist—are His acts in the past conceived as finite or infinite?