We rightly think that everything has a nature, namely a description of its substance and of all its essential properties and powers. In agreement with this general sense of the word ‘nature’, Aristotle's original Greek meaning of ‘physical’ is that which has its source of change within itself. If theism is true, and God is the source of our life and therefore the only thing with life in itself, then, strictly speaking, only God is physical! In this line of thought, Victor Reppert posts
I wouldn't even necessarily call God supernatural. There could conceivably be a science studying God's actions, based on which we could make predictions. If God would let us, we could even perform experiments on Him. What's wrong with this idea?Aristotle's aim was to distinguish it from what is artificial, which are those things that have sources of change outside themselves. Applying this principle as above would make all of the the rest of us beings as therefore ‘artificial’ (in some sense).
Actually, if you say that what we mean by supernatural is that it won't fit in to a mechanistic order, then of course God is supernatural. That's how Lewis defined it. But does everyone understand the term "supernatural" in that way? It seems like a lot of baggage is brought into the use of this term.
Some people do indeed view the world as an artificial tool or instrument of God, like a musical instrument which God plays to make music (us). Some think of God as like the author of a book in which are the 'artificial' characters, as I discussed previously.
However, this is not the everyday use of these terms. Since we commonly use the word ‘naturalistic’ or ‘physical’ to describe the basic sciences of today, we need to invent a new name such as ‘generalized-natural’ or ‘generalized-physical’ for the above sense of everything with a source of change within itself.
A ‘generalized physics’ would be the study of those things, and, when theism is assumed true, it will coincide with our theistic science. Both will be the study of everything that has a causal influence on the things in our world. In another variation on definitions, some philosophers define “physical things [as] those things that are postulated by a complete physics.” Theists claim that this must refer to the generalized sense of ‘physical’ which includes minds and even God.
So I am not going to use such a 'generalized' terminology, delightful though it may be.
I am therefore going to use ‘nature’ to refer to what is currently known as physical, including all material things and also whatever virtual or pre-geometric processes may be surmised in quantum gravity. Then, everything natural may be taken as itself dead and not living, however active or ‘subtle’ it may be. We will later see that natural things are energized and enlivened by something spiritual within them, but we will never need to identify spiritual as the ‘inmost of the physical’ and hence itself essential natural. The term physical, as I and most people use it, excludes what is mental or spiritual. And, of course, I will have to explain how they are related.
Adapted from chapter 7 of Starting Science From God.