Tom Mattson said:
I would think that it means that, as we learn more, the definition of what it means to be "physical" will change. At one time, it meant that material bodies were infinitely indivisible. Later, it meant that they were made of indivisible building blocks called atoms, that should in principle follow Newton's laws. Later still, it was found that those atoms have a structure, and that the constituents behave according to an entirely different set of laws than we had originally supposed. Then, we got to look inside the nucleus, and saw that those constituents behave according to a different set of rules, and so on.
Sorry, I just saw your post.
I have to agree with Fliption's point of needing to distinguish between physical and non-physical. One difference I often see between physicalist and non-physicalist perspectives is which came first. I would guess your view would tend toward saying that first came the big bang, and then everything else followed from the potentials created by that event.
I don't know if you followed my thread on panpsychism (BTW, thanks for the intervention), but at one point I posted a short contemplation on "substance monism"
https://www.physicsforums.com/showthread.php?t=30762&page=6&pp=15. It is a very common idea among non-physicalists that there exists some base substance (which I labeled
illumination -- if you don't mind, I'll continue to use that term for the base substance), which was never created and cannot be destroyed, which is light-like in essence as well as possessing an energtic temperment, and which exists in an infinite continuum (illumination is not baseless speculation, there is some evidence). The idea of substance monism, then, is that everything is a form of this basic, most fundamental "stuff" of existence. In it is all the potentials needed to create a universe (out of itself) and everything we find in the universe.
Now, the physicalist will say the universe began with the physical event of the big bang, but he cannot explain what caused the big bang, nor where all the stuff composing it originated. He can explain how energy moves things, but he can't explain what energy is. We can quantify oscillatory rates, but cannot explain why particles are such determined oscillators. In the end, the answers to those questions (and lots more) for the physicalist seem to boil down to "that's just how it is."
Okay, return to the primordial illumination concept. There we only need to say "that's just how it is" about one thing: illumination (or whatever the base substance is). Ockham's razor!

In terms of a theory, the final step is to infer that illumination is the
potential for what is most prevalent in and necessary to the existence of the universe, and then try to figure out what illumination would have to be like in order to take the "form" of a universe.
So it seems to me your answer that the definition of physical keeps expanding will only work if we don't look before the big bang. Yet we do have two origination theories which adherents attempt to make reasonable (I'm discounting supernatural possibillities; also, if I could have my way I'd also eliminate any purely rationalistic argument or model unsupported by evidence). One origination theory puts a physical event first, the other puts something we might conservatively label "absolute potentiality" first. We cannot explain the origin of the big bang or the stuff of matter. But we don't need to explain the origin of illumination.
Tom Mattson said:
And it is also the case that consciousness exibits characteristics that are physical-like. Even if you are of the persuasion that consciousness or free will (or whatever you want to call it) is "in charge" in that it dermines our brain states, instead of the other way around, it is still the case whatever this nebulous thing is, it has a physical effect on material bodies. That makes it physical, too. Now the problem is to develop a physical model that accounts for it, which I think is what SelfAdjoint was getting at.
It is very true that consciousness affects matter, and is affected by matter. But if you can temporarily accept the substance monism concept, then one can say that there is no
essential difference between the two. What is different, in that theory, is the conditions which define them. In the panpsychism model I used the analogy of how a mist sits on a warm lake at night. Right at the boundary between water and mist is some common point, yet there is also a point where water is liquid and mist is gas. So although identical in essence, conditions determine how H20's potentials will be manifested.
I don't think their (physical-consciousness) mutual influence must mean consciousness is physical; it could mean the physical, at the foundation, shares the same nature with consciousness and so allows a certain temporary compatibility (entropy ensures that it is impermanent). But if so then we still have the question of which is most fundamental, physicalness or consciousness.
Tom Mattson said:
Now the problem is to develop a physical model that accounts for it, which I think is what SelfAdjoint was getting at.
I agree that's what he is getting at, and I still maintain that is based on an a priori assumption about first cause. I've been trying to argue that it is actually easier to explain the universe if we have an uncaused first cause. Explanation "ease" also seems relevant to the question of which comes first, matter or consciousness? In the infinite ocean of illumination we are imagining, and considering the "hard problem" of consciousness, which would be easiest to first develop? Also, if consciousness developed first (and I don't mean some progeny of dogma, i.e., forever existing, all powerful, all knowing, supernatural, etc.), and we assume it has evolved far longer than the age of our universe, then doesn't that also add to the ease of explaining the development of our universe, especially when it comes to the evolution of life and consciousness?
The way I look at it, if neither the physical or non-physical side can offer convincing evidence of our origins, then all that's left is what most naturally accounts for the most unexplained things.