It was, then, the unsound rational premises and wayward allegorical readings adopted by those speculative theologians that propelled the later thinkers to the furthest reaches of unbelief, to outright denial of the Messengers, and to the ruin of both intellect and faith. Ibn Sīnā and his peers began dismantling the method those theologians had employed to prove that the world is originated and that the Maker exists—a method that rests on two pillars: the impossibility of an infinite regress of events, and the maxim that whatever holds true for each part must likewise hold true for the whole.

Abū’l-Ḥusayn al-Baṣrī, one of the sharpest minds among them, makes the very foundation of religion depend on this syllogism: if every single event came to be after not having existed, then the totality of events must also have come to be—just as, if every individual Zanj is black, then the Zanj collectively are black. Abū’l-Maʿālī al-Juwaynī and those of his school add that to affirm origination while denying divine action in pre-eternity is to conjoin two contradictory propositions.

Their challengers—both the adherents of the prophets and the followers of the philosophers—replied: the distinction between a species and its individual instance is self-evident. What reason rules out is either the existence, in pre-eternity, of a particular originated entity such that it would be both originated and eternal, or the existence of the entire collection of events in pre-eternity such that every event would be eternal. As for an everlasting succession of events, one after another—as events will indeed succeed one another without end in the future—nothing in the intellect renders this impossible, and one cannot, for the point at issue, draw a decisive distinction between the past and the future.

Furthermore, not every aggregate is necessarily described by the same attribute that describes each of its members. It may be so described when no new property arises from their combination, but it may not be so described when a new property does arise. The first case is exemplified by grouping together existents and non-existents, possibles and impossibles—their combination does not lift from them the rulings entailed by those attributes. The second case is illustrated by assembling the parts of a line, a surface, a body, or any extended thing: their union yields a property not found in the parts considered in isolation.