Aquinas's Fifth Way

[Neo-Scholastic]

You can always ask why [nature is regular]. And you can only answer by either appealing to science or theology. Give me one good reason why anyone should ever even consider the latter as anything but speculation based on mere assumption.

Natural science already takes causality as a given. The problem lies at a higher level of inquiry, mainly metaphysical (or as you say theological). Speculations and assumptions are not grounded by reason, which is the main tool of philosophy.

But there is an explanation [for natures regularity]; the cause is not changing…so there is no mechanism evident that would cause the effect to change.

So, why don’t causes produce inconsistent results?

You're either positing the existence of an effect (that changes the effect of another effect) without a cause, or you're positing a cause that we're unable to apprehend, creating the same effect.

I say that there is a base cause that that can be apprehended by means of reason, something fundamental that directs causes to their effects. Without such a fundamental cause, there will be (as you point correctly point out, like Hume before you) an infinite recess within the causal chain.

Your very first premise is that things do not change without some extant force acting upon them,… either…you're positing an effect without a cause which violates your first premise

The first premise acknowledges that some substances, like plants and animals, do have within themselves the power to change. This objection does not apply.