in its complete form. For otherwise, the thing would remain contingent even after the determining factor existed, admitting either existence or nonexistence, and would then require a further determining factor. This entails an infinite regress, which ends only when there exists a complete determining factor that necessitates the outcome.

Here people disagreed. One group, including Muhammad ibn al-Haysam al-Karrāmī and Mahmūd al-Khwārizmī, held that a contingent thing becomes more likely to occur, but its occurrence does not become necessary.

Most of the Muʿtazilah and Ashʿarīs said:

Rather, its occurrence does not become more likely. Instead, an agent possessing power—or possessing both power and will—gives preference to one of two equivalent alternatives without a determining factor.

Others recognized that this consequence was unavoidable. They therefore acknowledged that, when the complete determining factor exists, the effect must exist, and that, when the complete motive is present together with power, the act must occur. Abū al-Husayn al-Basrī, al-Rāzī, al-Tūsī and others acknowledged this. Many of the earlier speculative theologians affirmed a necessitating will, holding that will entails the existence of what is willed.

The philosophers raised this objection against the speculative theologians, but maintained that the effect accompanies the exercise of causal influence, so that the two exist together in time. Many people know only this view and that view