the agent acts by choice, complete power and a decisive will are indispensable. The contingent thing cannot come into existence without them, and whenever they are present, the contingent effect must come into existence. Whatever Allah wills comes to pass, and whatever He does not will does not come to pass. Thus, whatever Allah wills must exist, and whatever He does not will cannot exist. If the complete efficient cause is present for a contingent thing, its existence becomes necessary through another; if it is not present, its existence is impossible because the complete efficient cause is absent. Its existence, therefore, can come about only through another.

As for its nonexistence, it has been said that this too must have a cause. This is the position of Ibn Sīnā and his later followers, who say that neither of the two alternatives for a contingent thing can prevail over the other without a determining factor.

It has also been said that its nonexistence does not require a cause. This is the position of the well-known Sunni scholars of rational inquiry, such as al-Qādī Abū Bakr, Abū al-Maʿālī, al-Qādī Abū Yaʿlā, and Ibn ʿAqīl. It was also al-Rāzī’s final position: he sometimes adopts the view of one group and sometimes that of the other, but this was the later of his two positions.

According to them, nonexistence does not require a cause. When it is said, “It does not exist because its cause does not exist,” this means that the nonexistence of its cause entails its own nonexistence—not that the former brings about the latter. Rather, when its cause is absent, we know that it does not exist. This is therefore evidence of its nonexistence, not that one of the two instances of nonexistence