It has therefore been established that He has never ceased to possess power, and that whatever falls under His power has never ceased to be possible. Hence the possibility of an act has no starting point. If an act has always been possible, then its being eternal is conceivable; if not, its eternality is impossible.
It follows that to affirm the eternity of possibility while denying the possibility of eternity is to unite two contradictory propositions. Their own keen-sighted scholars concede this. What drove them into so awkward a position was their claim that the act—whether it be speech or any other act—had once been impossible and only later became possible. The first to utter such a claim in Islam were the Jahmiyyah and the Muʿtazilah. None of the Imams of Islam ever held it, nor is there any report—wording or sense—from the Prophet (peace and blessings be upon him), his Companions, or the Followers that supports it.
Having advanced this doctrine, they were forced to respond to their opponents’ objection: “Possibility has no beginning; for were it to have a beginning, intrinsic impossibility would turn into intrinsic possibility without a cause.” They replied, “We postulate that the possibility of coming into being has no beginning,” or, “Possibility—on condition that the contingent actually occurs—has no beginning.” The result, however, is that the possibility of occurrence both has a beginning and has no beginning—a patent contradiction.
Indeed, for everything whose occurrence is necessary and whose pre-existence is impossible, the possibility of its occurrence has a starting point, and it is absurd to hold that this possibility has no beginning. Whether the possibility is conditioned by the agent or by the recipient, once the possibility of occurrence has a first moment, it cannot be without one. Although the occurrence of things that have a beginning is intelligible with respect to particular events, not a single created being exists whose possibility of coming into existence lacks a first moment. It is impossible for something to be produced in time while the possibility of its production is eternal.