impediments. Otherwise, if it remained as it had always been, no act could proceed from it, since singling out certain times for action requires a cause of specification. The same argument applies to this newly arising occurrence as to the world as a whole. If an act proceeds from it, it cannot begin to do so after previously not doing so, lest the aforementioned impossibility follow.

In short, either it is a complete cause of the act or it is not. If it is a complete cause, the act must be simultaneous with it. If it is not a complete cause, something new must arise by which it becomes a complete cause. The same argument applies to this newly arising thing as to the world: if its cause is complete, it must be simultaneous with its cause; if its cause is not complete, something new must arise, and an infinite regress necessarily follows.

This argument hinges on the claim that an effect must be simultaneous with its complete cause, and that the cause cannot act after not having acted. They uphold this argument, and people have answered it sometimes by challenging its premises and sometimes by presenting counterarguments. At times, they deny that the effect must be simultaneous