existence and nonexistence coinciding more than once. All of this is impossible.

The same kind of circular dependence can involve one thing being the agent that produces another, its efficient cause, its final cause, or the like. For an agent, a cause, or anything of this kind cannot be its own act; how, then, could it be the agent that produces its own agent? Likewise, an efficient cause cannot be its own efficient cause; how, then, could it be the efficient cause of its own cause? Similarly, the final cause that the agent brings into existence is produced by that agent and owes its existence to it, not to itself. If it cannot be its own effect, how could it be the effect of its own effect?

These and similar forms of circular dependence entail a thing preceding itself or preceding what precedes it; being the agent that produces its own produced self or its own product; being the cause of its own caused self or of the effect of its own effect; or being an effect and product of itself, or of its own effect and product. All of this is plainly impossible. Hence, rational people agree on its impossibility.

As for infinite regress in effects, conditions, and the like, there are two well-known positions held by different groups. Infinite regress in agents, efficient causes, and the like, however, is undoubtedly impossible.