I realize that this is more of an Aristotelian/Thomistic argument than Leibnizian, but I can't think of another sub-forum to post this. Any feedback is appreciated.

1. Everything in motion is moved by another.

2. The series of movers either proceeds to infinity, or has a first mover.

3. The series cannot proceed to infinity.

4. Therefore, there exists a first mover.

The argument is obviously valid, but some have challenged the premises' soundness. I think for the most part, however, these objections are based on misunderstandings.

(1) is often objected to by pointing out that quantum fluctuations may be random. I say *may be* because there are deterministic hypotheses that attempt to explain QM. However, I think we can weaken the strong causal principle from determinism to something more palatable for skeptics. We might defend (1) by appealing to the metaphysical principle that being cannot arise from non-being - that is, something cannot come from nothing.

(2) shouldn't be controversial, since it is just enunciating the two available options we have. I think (3) is the key premise, therefore. This argument should not be confused with the KCA, which denies that a temporal infinite regress is impossible. Instead, this argument is claiming that an ontological infinite regress is impossible. Take the human body, for example. At any finite moment of time (i.e. the present), the human body is being sustained by its organs, its organs by cells, its cells by molecules, and so forth. The question is whether or not this ontological (re: hierarchical) series can proceed to infinity.

I would argue that this series cannot proceed to infinity. The reason why is because it would require an infinite series to move something within a finite period of time; but, it would take infinite time for an infinite series to move anything at all. Hence, the series of movers must be finite, and must have a first mover.

Thoughts?