Nature is in one sense easy to compared to art, and in another sense it is distinguished from it. The determined and ordered actions of natural bodies are easily compared to machines; but at the same time “nature” is first understood in English as woodland areas, or places otherwise untouched by the human hands.
Nature first means birth- that eminently knowable process of a baby coming out of a mother. By moving from effect to cause, the word nature got applied to the mother herself (there is still a hint of this in the Latin root for mother “mater”: the mater was what gave us the idea of the matter- that from which the child or anything else came to be. Matter is the first universal cause we know of nature, so much so that many thinkers never see another one) By moving from cause to a more particular effect, the word “nature” got applied to the very thing that came forth, and especially whatever it had within it that made it come forth. This last sense of nature is nature as an interior principle of going from one this to that, which is the sense that Aristotle defines in the second book of the Physics. Nature on this account is the first, per se cause of motion or rest in that in which it is.
Nature is the the first thing, and in this sense it is innermost. Even though nature as defined is not the same as substance, its meaning will easily shift to substance because nature has the sense of being before all other things; for all that is other than nature is somehow outside of it, like an accident is outside of substance.
This sense of nature as innermost sharply distinguishes nature from art; for our art must act upon something and presuppose something that already has its own nature. Our art must be secondary and derivative, simply because it creates from something. And this is why nature is seen as a properly divine work: for in order to explain how nature came to be, we must see it as the work of a being that creates without presupposing anything- i.e. from nothing. And this all men call God. To impute the generation of a natural thing, as natural, to any other cause would be to confound the distinction between nature and art.