George Berkeley, in A Treatise Concerning the Principles of Human Knowledge (1710), gave the following definition:
“By Matter, therefore, we are to understand an inert, senseless substance, in which extension, figure, and motion do actually subsist.” (pt. 9)
Consider the following from Colin McGinn (transcribed from here):
“It’s very difficult to get across to people who are religious, that when you’re an atheist you mean you don’t believe in anything [like God] whatsoever. […] You don’t believe in anything of that type. Nothing supernatural[.]”
I think that McGinn’s clean conceptual distinction is problematic. “Nature” is tied to what is “physical.” How do we know whether something is physical? My sense is that: we know from whether it is part of our paradigmatically physical causal network. This is just to say, whether it interacts with the physical causal network. This is how we come to ascertain that something is “physical.” We do not say that something must conform to a specific understanding we have a priori of, say, regularity, in order to be physical.
Basic idea: Whatever has a robust evidentiary basis and interacts with paradigmatically physical things will come to be classed as “physical,” whether it be by ferretting out the true nature of the phenomenon and discovering it works by recognized physical principles, or by expanding the concept of “physical.”
For example, George Berkeley’s definition of “matter” above is not the current definition. Our concept of matter changed due to physical investigation.
(Also see here.)