And the proof he gave to refute an infinite regress is likewise confined to this case. It would therefore have been preferable to discuss this issue first. However, since he intended to address it elsewhere, namely in the fifth section of this book, he was less rigorous about it here.”

I say:

It was reasoning of this kind that led al-Āmidī and others to include this case in the argument. Yet there is no need for it; what Ibn Sīnā stated is sufficient.

The proof he gave to refute an infinite regress of causes rules out such a regress whether the causes are assumed to coexist or not, as his words have already made clear. He does not allow an infinite regress of causes, whether successive or otherwise. He allows only an infinite succession of events. In his view, those events are conditions for the occurrence of subsequent events, not causes, nor causal factors understood as causes. He does not allow each contingent thing to derive its existence from a preceding contingent thing at all. Rather, he allows its existence to be conditional upon the existence of a preceding contingent thing. There is a well-known distinction between a cause and a condition.

This is the source of al-Rāzī’s error in this objection. Thus, the others who discussed the refutation of an infinite regress of causes had no need to mention this case at all. They do not say that a contingent thing or an event preceding another contingent thing or event is also its cause, or that the latter owes its existence to it. They say only that it is a condition for its existence.