Others maintain that it is sufficient, for something to come into existence, that there be a capable Agent—one who can either act or refrain and who acts by choice. According to them, His power alone, or His power together with His will, or His power together with an inner motive, suffices to tip the balance between the two possibilities without any further determinant.

Some thinkers distinguish between a merely capable agent (qādir) and a necessitating cause (mūjib). They hold that a necessitating cause does not produce its effect unless it is complete, such that the effect follows from it inexorably, whereas the capable agent can bring about an effect only as a matter of possibility.

The point at issue is that al-Rāzī’s argument stands firm under all these assumptions; however one defines “the agent,” his reply remains sound. For this particular contingent entity—whether a human being, a horse, a fruit, or anything else that appears daily—must have a producing cause. Should that cause itself be contingent, the discussion of why it came to be is identical to the first question, and one would have to posit an infinite succession of agents, each acting upon another. If you prefer, you could say that this entails postulating an infinite number of causes and effects all at once; or that it demands positing agents and their acts without limit; or creators and creatures without end; or causes and their consequents in an endless series.

On every reckoning, if the immediate entity is contingent, then there must exist causes and effects that are infinite in number, existing simultaneously. Al-Rāzī speaks of “simultaneously” because the assumption is that the agent producing this contingent thing is itself contingent, not eternal. Should someone object, “Could it not be that the agent of this thing was produced before it, and the agent of that prior one produced before it, and so on ad infinitum?”