, could itself have another cause, and so on. On this supposition, we would have nothing to demonstrate the impossibility of this infinite regress, since it amounts to affirming necessarily existent things, each having a cause. Their totality is also necessarily existent, although both the totality and each of its members are effects. This is what ‘contingent’ means in this later terminology: for them, something contingent can be necessary, necessarily existent, and incapable of nonexistence, while still being caused by something else.
On this supposition, then, there is nothing impossible about the existence of causes and effects, each necessary and necessarily existent, and called contingent because it is an effect—not because it has come into being and depends on an agent.”
[Ibn Rushd’s response to al-Ghazālī and Ibn Taymiyya’s commentary]
The reality is that they have posited an infinite series of things, each necessarily existent and incapable of nonexistence, yet each an effect. On account of this, they called each one contingent and said:
“It admits both existence and nonexistence.”
Yet they cannot then establish that even one of these things depends on a cause, let alone that they all do, since they are all assumed to exist necessarily and to admit no nonexistence. It is conceivable that such a thing depends on an agent, and the matter returns to the contingent being they have posited—namely, that which is necessary, necessarily existent, eternal, and beginningless: does it depend on an agent and a determining cause that favors its existence over its nonexistence?
It has already become clear that they have no proof of this. Rather, all rational people say that such a thing does not depend on an agent.
Thus, when they based their proof of the Necessary Existent on establishing this contingent being—as Ibn Sīnā, al-Rāzī, al-Āmidī, and others did—they could not furnish proof that this contingent being, understood in this sense, depends on an agent. Objections were raised against this contingent being that they could not answer, some of which have been mentioned elsewhere.