One often talks of the “uniformity of nature” in the context of the problem of induction: the striking and prima facie puzzling fact that the laws of nature that hold in our local contexts also hold in non-local contexts.
That’s a “horizontal” uniformity of nature. But there is also a very interesting “vertical” uniformity of nature. This is a uniformity between the types of arrangements that occur at different levels like the microphysical, the chemical, the biological, the social, the geophysical and the astronomical. The uniformity is different from the horizontal one in that, as far as we know, there are no precisely formulable laws of nature that hold uniformly between levels. But there is still a less well defined uniformity whose sign is that same human methods of empirical investigation (“the scientific method”) work in all of them. Of course, these methods are modified: elegance plays a greater role in fundamental physics than in sociology, say. But they have something in common, if only that they are mere refinements of ordinary human common sense.
How much commonality is there? Maybe it’s like the commonality between novels. Novels come in different languages, cultural contexts and genres. They differ widely. But nonetheless to varying degrees we all have a capacity to get something out of all of them. And we can explain this vague commonality quite simply: all novels (that we know of) are produced by animals of the same species, participating to a significant degree in an interconnected culture.
Monotheism can provide an even more tightly-knit unity of cause that explains the vertical uniformity of nature—one entity caused all the levels. Polytheism can provide a looser unity of cause, much more like in the case of novels—perhaps different gods had different levels in nature delegated to them. Monotheism can do something similar, if need be, by positing angels to whom tasks are delegated, but I don’t know if there is a need. We know that one artist or author can produce a vast range of types of productions (think of a Michelangelo or an Asimov).
Any case, the kind of vague uniformity we get in the vertical dimension seems to fit well with agential explanations. It seems to me that a design argument for a metaphysical hypothesis like monotheism, polytheism or optimalism based on the vertical uniformity might not have some advantages over the more standard argument from the uniformity of the laws of nature. Or perhaps the two combined will provide the best argument.