I'm gonna go with mass and/or energy. I'm sure a thoughtful comment would be more detailed than that, but that is probably sufficient.Physicists are coming up with new particles all the time. What makes them physical as opposed to not physical?
You seem to have focused out the word "physical", which is the important word. "Real, therefore part of nature" is not an axiom I would agree to, and is really just assuming the conclusion here.Yes, but if something can interact with what is "real" then that something must also be every bit as real, and therefore part of nature.
If it is completely separate from what is "real", then it may exist but is functionally irrelevant to us, because it has no effect on us whatsoever.
Like, you all seem to have a different definition of nature than human civilization has for millenia. And the definition you've all chosen inherently precludes the supernatural. "Anything that is real is part of nature" means by definition that anything supernatural isn't real. To say then that you don't believe in the supernatural is tautological, basically "everything that is real is real". Once we account for differences in how the terms are being used, you're not even stating a disagreement, you're just telling me to use your terms rather than those used by centuries of great thinkers who discussed nature as a subset of reality (rather than all of it) for useful communicative reasons.