They are told:
This is conceivable if (1) the receptacles came into being from something other than Him, as in the case of a ray proceeding from the sun and as they maintain regarding the Active Intellect. But if He is the agent that brings about both the receptacle and what is received, and both the condition and what depends upon it, and He is a complete, eternal cause of whatever proceeds from Him (2), then His entire effect must accompany Him, and nothing may lag behind Him. For it is impossible that He should become an agent after not having been one without bringing something into being; yet His bringing something into being (3) while being (4) a complete, eternal cause is impossible. It is likewise impossible for Him to be the cause of temporal events as a class while no act that subsists in Him comes into being.
Moreover, it is impossible for the world to proceed from two agents, whether they jointly produced all of it or one produced part of it and the other another part, as has been explained at length elsewhere (5). This is undisputed, for no rational person has maintained that the world proceeded from two beings equal in attributes and actions.
Nor has any rational person said, “The eternal foundations of the world proceeded from one, while its temporal events proceeded from another.” For the world is never devoid of temporal events (6), and it is impossible to produce that which has a necessary concomitant without its concomitant. If someone else were the agent that produced its necessary concomitants, neither agent’s act could be completed without the other. This would entail circular dependence between the two agents: each [one] (7) of the two lords would become a lord only through the other, become powerful only through the other, and become an agent only through the other. Thus, neither