Thus Ibn Sīnā took their argument and transferred it to the domain of possibility and necessity, maintaining that what is possible cannot be determined one way rather than another without a determining factor, so as not to contradict his position that the world is eternal. He maintained that the world is the effect of an eternal cause that necessarily entails it. Yet he forgot what he and his predecessors had established in logic: that whatever can either exist or not exist must have come into being, whereas whatever exists perpetually, without beginning or end, must be necessary, not something that can either exist or not exist. What they stated in logic is agreed upon by all rational people.

He also took their weak assertion that an agent endowed with power and choice brings events into being without any newly arising cause, and made it an argument for the eternity of the world by demanding that they identify a cause for its coming into being. Yet the consequences entailed by his position, which exposed its falsity, were graver than those entailed by theirs, which exposed the falsity of their position. For if the world proceeds from a cause that necessarily entails it, and nothing of the effect of such a cause can come after it, then it follows either that no events come into being in the world, or that events have come into being without an originator.

This involves a far greater instance of one alternative being determined without a determining factor than that upon which they based their proof of the existence of the Necessary Being.

Their position therefore entails the invalidity of the argument by which they established the Necessary Existent, the invalidity of inferring an originator from what comes into being and the Necessary from the possible, and that events have come into being without any originator whatsoever.