This premise on which they based their argument—that a contingent being may be beginningless, eternal, necessary, and necessary through another, and that a necessary, beginningless, eternal being whose nonexistence is impossible throughout the eternal past and future may be either necessary through itself or contingent in itself but necessary through another—is an innovation introduced by Ibn Sīnā, in which he opposed the generality of rational thinkers, both his predecessors and others.
Aristotle and the other philosophers explicitly stated that whatever is contingent, admitting both existence and nonexistence, can only be originated, whereas whatever is perpetual, beginningless, and eternal must be necessary and cannot be originated.
Ibn Sīnā and his followers agreed with them on this, stating it in several places in their discussions of logic. Elsewhere, I have quoted his words from his book entitled al-Shifā (The Healing) and other works, as well as the words of others.
Yet Ibn Sīnā and his followers contradicted themselves. When they found that the speculative theologians divided what exists into the necessary and the contingent—by the contingent, they meant what is originated—they followed their approach to this division, but included within the contingent that which is beginningless and eternal. They forgot what they had stated elsewhere: that whatever is contingent can only be originated.
What these thinkers and the other rational thinkers stated thus provided evidence that everything besides Allah Most High is originated, coming into existence after not having existed. For it has been established that Allah alone is necessarily existent and exists through Himself, and that everything besides Him depends upon Him.
What Aristotle and the other rational thinkers stated refuted what Ibn Sīnā and his followers said about the contingent, concerning which they contradicted themselves. In turn, what Ibn Sīnā and his followers among the rational thinkers stated about that which is necessary through itself refuted what Aristotle and his followers—and Ibn Rushd as well—maintained,