Then the eternalist philosophers, such as Ibn Sīnā and others like him, said:
“An infinite succession of events and their perpetual continuation are necessary, because an event cannot come into being without a cause. Thus, the genus of events cannot come into being without a cause that itself comes into being. Each event has a cause that itself comes into being; the genus is therefore eternal, and consequently the world is eternal.”
Abū al-Husayn al-Basrī and others like him among the Muʿtazilah, along with similar speculative theologians, said:
“An infinite succession of events is impossible, because every event is preceded by nonexistence. The genus must therefore be preceded by nonexistence. It follows that whatever is never free of events must have come into being. Bodies are never free of events, so they must have come into being.”
The very premise shared by both groups is false: that the possibility of an infinite succession of events entails the eternity of the celestial spheres, the world, or anything within the world.
The eternalist philosophers acknowledge its falsity even more readily than the Muʿtazilah. For an infinite succession of events and their perpetual continuation entail neither the eternity of any individual event, nor the eternity of the heavens and celestial spheres, nor that of anything within the world.
The philosophers concede that an infinite succession of events does not entail the eternity of any individual event, and that such a succession is possible—indeed, necessary.
They may therefore be asked:
“Granted that events have always continued to occur one after another, on what grounds do you claim that the celestial spheres are eternal? Why could they not have come into being after earlier events?”
Indeed, they may be told:
“This invalidates your position. For if events form an infinite succession, they cannot proceed from a complete cause that necessarily produces its effect, since no part of the effect of a complete cause can be delayed after it. Events, however, do occur later. Thus, they cannot proceed from a complete cause, whether through an intermediary or without one.”