So the interaction problem is either a problem for Naturalism or, more likely, the argument is just a disposable stage toward the actual truth, sc. the disagreement over whether the fundamental agencies are intelligent or “brute” and “blind”. But even this might not say enough: recall among those who held that the first mover was intelligent there was also a belief that there were brute or blind universal causes. For Aristotle, it was not just the prime mover who was a universal cause but also the celestial bodies, the first being an intelligence and the second not. This means that we need to push the argument to another stage: classical physics did not change the non-interactive causes from intelligent to blind ones, but rather assumed that the blind ones were sufficient.
Sufficient for what? It’s hard to see what we would mean in a way that Aristotle wouldn’t agree with. Nature was a totality for him too, a large sphere containing all that there was of space and time or metrical and sensible matter. There was nothing of the same kind beyond it, and so explanations of natural things came to an end in the blind activity of the universal causes. But he believed in a prime mover for all that.
For both the Medievals and the Moderns, the idea of nature remains what is determined to a single course, and so lacking the sort of indetermination that intelligence has. But why posit indeterminate causes (free ones) for determinate activities? Why bother having angels move stars if all they will do is move them predictably on one track forever? One supposes that this is exactly the sort of thing that someone would automate. More to the point, does one even need intelligence for the sort of universal causes we now have? One supposes we would need something to move the stars and the celestial spheres, but one doesn’t need anything to move energy or gravity. But this can’t be quite right either since, for Aristotle, the planets revolved just as naturally as stones fall down. Why did he posit a mover for what moved by nature?
In one sense, he doesn’t need to, which is exactly the point made above. If we want to explain is natural motion, we can reduce it to whatever can move another thing by its very nature: the celestial bodies, gravity, or energy. Movers are not necessary beyond his because to explain some sort of indeterminacy in the power of the thing to move. Putting intelligence as a motive power behind the stars, gravity, or energy does not mean that these things are inert – it’s their very nature to cause others to move, and to be unable ever not to move others. All these things preserved a conservation law, and could not be engendered or corrupted into their elements. In explaining nature, it suffices to link the contingent to the necessary.
But necessity is a hierarchical thing: there are things necessary from another (NA) and necessary in themselves (NT). The truths we know are a good example of NA’s: they must be, so long as there are minds to think them. But if we can divide the two, it makes seems that the contingent: NA :: NA : NT. But this would mean that the scientific attempt to range the contingent under the necessary is just the first move in a larger analogical proportion: what the various mobile and changeable things of the universe are to energy, so energy is to that reality necessary in itself. This is exactly the claim of the Third Way (so often misunderstood as an argument from mere contingency).