That is an epistemological notion of the physical. Perhaps a metaphysical definition would be that an event or object is physical if and only if it has a spatiotemporal location within some reference frame.

We also describe laws as physical of course, and they don't seem to be covered by either of our definitions, but presumably the idea is that a law is physical if and only if it treats of physical events and objects.

My concept is the same as yours. I reached the conclusion a few years ago that the only concept of 'physical' that made sense to me is an epistemological one. Thus, what is physical will change over time as our scientific theories change. Further, the concept of physical that we have in 500 years time may not even be intelligible to us at present, if it uses concepts we do not currently have.

A problem with using a definition based on spatiotemporal locations is that the wave function of quantum mechanics does not have a spatiotemporal location, so we then get embroiled in a common debate within QM about whether the wave function is 'physical'. This becomes even more stressed when we consider non-local interpretations of QM such as Bohm's with its pilot wave.

Another thing I like about the epistemological definition is that it makes it possible for everybody - materialists and supernaturalists alike - to agree that there are probably non-physical things.

My concept of the non-physical is phenomena that cannot be detected by our senses and the scientific extensions of our senses and which cannot be explained by existing scientific paradigms. — johnpetrovic

You're describing something that possibly doesn't even exist. How does one provide evidence for things that our senses and scientific instruments can't get at? To ponder the existence of such things would be a waste of time.

The non-physical is associated with our current state of scientific knowledge. For example, prior to the work of Maxwell and Hertz, electromagnetic radiation was non-physical, but became physical as a result of the knowledge that they generated. At the present time, self-aware consciousness is non-physical.

What is your concept of the non-physical? — johnpetrovic

This is related to the "supernatural" as science provided natural explanations for environmental phenomenon, the supernatural explanations were eventually abandoned.

This kind of description of "non-physical" is arbitrary and meaningless. By whose standards of scientific explanations are we measuring - 21st century humans? 15th century humans? Humans from 5,0000 BC? or aliens? If aliens have explained consciousness, doesn't that mean that consciousness is physical and we are simply ignorant - just as we were when we had our "supernatural" explanations?

Another thing I like about the epistemological definition is that it makes it possible for everybody - materialists and supernaturalists alike - to agree that there are probably non-physical things. — andrewk

I would have thought if a materialist agreed there were non-physical things then they would be abandoning materialism, wouldn’t they? Materialism means ‘there are no non-physical things’.

One kind of materialism is mind-brain materialism, I think that is consistent with the belief that there are non-physical (i.e. abstract) things (numbers/properties etc). At least, it doesn't seem obvious to me that materialism is committed to nominalism.

Oh, I’m pretty sure it is. That general idea is called mind-brain identity theory, I think. It says that thinking might be ‘supervenient’ on neural activity, where ‘supervenience’ means something like the upper-level properties [i.e. thought and cognition] are different from the lower-level [i.e. neurobiology] but are ultimately dependent on them.

I would be very surprised if any of those kinds of philosophers accepted the reality of abstract objects. But I’m willing to be shown I am wrong.

I think that a non-physical thing is that has not physical properties, so physics is not able to account it. For example, mathematical and logic systems, natural languages, etc.
Regarding conscience, it seems to be the physical thing that make possible the existence of non-physical things.

I would have thought if a materialist agreed there were non-physical things then they would be abandoning materialism, wouldn’t they? Materialism means ‘there are no non-physical things’. — Wayfarer

If I ever encounter a materialist, I refer them to the 2nd law of thermodynamics. Then they are forced to join the physicalists.

You might expand on that. I had the idea that physicalism and materialism were basically two different names for the same general position.

My concept of the non-physical is phenomena that cannot be detected by our senses and the scientific extensions of our senses and which cannot be explained by existing scientific paradigms. The non-physical is associated with our current state of scientific knowledge. For example, prior to the work of Maxwell and Hertz, electromagnetic radiation was non-physical, but became physical as a result of the knowledge that they generated. At the present time, self-aware consciousness is non-physical.

What is your concept of the non-physical? — johnpetrovic

I have never encountered the claim that the scientists working on e.m. radiation thought they were trying to understand something non-physical before. I just doesn't make sense.

I don't think I am misrepresenting physicalism too much by describing it as the metaphysical assertion that everything that is instantiated in Reality is physical. This includes everything we have discovered, and everything we have yet to discover.

There are actually more examples of entities that were once thought of as physical, but were discovered not to exist - the ether, flogiston, elan vital ...

Non-physical things we have discovered so far, are objects that only exist in symbolic form, such as the objects and necessary truths of mathematics.

As for the mathematical truths not yet discovered, then I am forced to conclude, by my preferred epistemology, that they already exist.

If I remember rightly (and I'm not 100% certain I do) David Armstrong was a mind-brain identity theorist (of the functionalist kind I believe) but argued throughout his life against nominalism. Of course, that doesn't mean he was correct to do so - there may have been hidden inconsistencies in his position - but it looks coherent to be both a materialist about the mind and yet a realist about some kinds of abstract things (laws of nature for instance).

Sorry, I should not say "abstract things" more like "non-particular things" - i.e. things that cannot be identified uniquely by their spatiotemporal location.

I don't think I am misrepresenting physicalism too much by describing it as the metaphysical assertion that everything that is instantiated in Reality is physical.

Unless you expand on what you mean by "physical" that description is unilluminatingly circular.

This is a reasonably clear article casting doubt on the usefulness of the notion of physicalism in philosophy (a little dated now perhaps, but makes some clear points):
There is no question of physicalism

You might expand on that. I had the idea that physicalism and materialism were basically two different names for the same general position. — Wayfarer

You are probably right, but I feel compelled to draw the distinction. Materialism seems to indicate that not only is everything constituted of mater interactions, but that is all there is.

Physicalism seems to admit, in accordance with the 2nd Law, that pattern is real, causal, and as fundamental as matter.

If I remember rightly (and I'm not 100% certain I do) David Armstrong was a mind-brain identity theorist (of the functionalist kind — MetaphysicsNow

I think that is right. I was enrolled as an undergrad at UniSyd when he was head of ‘Traditional and Modern’ - in those days, the Philosophy department was split between that school [roughly, OxBridge positivism] and General [marxist and Pomo.] I was in the no-man’s land trying to understand enlightenment. I fairly soon as absconded to Comparative Religion which was far more congenial to my outlook [although I was always treated with utmost courtesy by everyone I learned from at that Department, and have very happy memories of it.]

Anyway, I never really studied Armstrong as I was of the view that ‘materialist theory of mind’ wouldn’t contain anything of interest. I have briefly perused some of the SEP entries on him in the years since, and see no reason to revise that opinion. [it is interesting that many of the prominent materialist philosophers are or were Australian; I suppose it might be connected with the generally secular and irreligious attitude of Australian society.]

That paper looks interesting, will look at it later.

Physicalism seems to admit, in accordance with the 2nd Law, that pattern is real, causal, and as fundamental as matter. — tom

My view is that science doesn’t explain itself; the natural laws and regularities which science assumes and relies on, are not themselves explained by science. That is the sense in which they transcend science - they are the basis of scientific explanation, but are not themselves explained by science. It’s a bit of an Indian rope trick - the rope extends up to the clouds, we can’t really see what supports it, but, damn it, there it is.

My view is that science doesn’t explain itself; the natural laws and regularities which science assumes and relies on, are not themselves explained by science. — Wayfarer

Science doesn't assume or rely on any such inductive principle.

Of course it does. If physical outcomes couldn’t be predicted by mathematical formulae, then science couldn’t get out bed in the morning. [That is precisely why Hume’s ‘criticism of induction’ was said to undermine science by Bertrand Russell in HWP]

it is interesting that many of the prominent materialist philosophers are or were Australian;

Bernard Williams once made a "joke" that whilst Australia wasn't the only place where materialist theories of mind were believed, it was the only place where they were true.

Bernard Williams once made a "joke" that whilst Australia wasn't the only place where materialist theories of mind were believed, it was the only place where they were true. — MetaphysicsNow

Of course it does. If physical outcomes couldn’t be predicted by mathematical algorithms, then science couldn’t get out bed. [That is precisely why Hume’s ‘criticism of induction’ was said to undermine science by Bertrand Russell in HWP] — Wayfarer

Science doesn't use induction or any other mythical principle.

I refer you to Logic of Scientific Discovery, by Karl Popper.

Science doesn't assume or rely on any such inductive principle. — tom

Sorry, I think you may be confusing the 2nd Law with dialectical materialism.

Bernard Williams once made a "joke" that whilst Australia wasn't the only place where materialist theories of mind were believed, it was the only place where they were true. — MetaphysicsNow

:lol: I studied near David Chalmers and asked him to come onto the old PF forums, but I can assure you that this is no joke.

Unless you expand on what you mean by "physical" that description is unilluminatingly circular. — MetaphysicsNow

That's quite funny. You, of course are completely confident in the definition of "metaphysical" or even "instantiated".

Try reading all of the post.

Sorry, I think you may be confusing the 2nd Law with dialectical materialism. — TimeLine

I'm quite familiar with the 2nd Law of Thermodynamics. It might be informative if you could use an inductive principle to derive it, though? I don't think dialectical materialism will help in this case.

What I meant is that the conflict with the 2nd law is only applicable to dialectical materialism but that materialists believe in the 2nd law since the only violation is cosmological; sorry, I may be wrong about what you are trying to convey. Can you clarify?

Try reading all of the post.

I did try, and here's something else wrong with it:

I have never encountered the claim that the scientists working on e.m. radiation thought they were trying to understand something non-physical before. I just doesn't make sense.

You don't seem to understand how electromagnetic radiation was discovered. Maxwell gave us electromagnetic radiation as a new theoretical concept, Hertz gave us its empirical confirmation. Prior to Maxwell, physicists working in electricity and magnetism worked - like Maxwell - on electromagnetic fields. Maxwell brought together the previous work of those other physicists into "his" four field equations. It turned out that those equations have a solution which describes the wavelike propagation of electric and magnetic energy in a vacuum at the speed of light. After Maxwell's theoretical discovery/invention of electromagnetic radiation, that radiation became an object for physical research, and most famously Hertz's which culminated in confirmation of Maxwell's theory.
That's entirely consistent with the OP's suggestion that electromagnetic radiation is non-physical right up to the point where Maxwell's conceptual apparatus suggested its existence.

You don't seem to understand how electromagnetic radiation was discovered. Maxwell gave us electromagnetic radiation as a new theoretical concept, Hertz gave us its empirical confirmation. Prior to Maxwell, physicists working in electricity and magnetism worked - like Maxwell - on electromagnetic fields. Maxwell brought together the previous work of those other physicists into "his" four field equations. It turned out that those equations have a solution which describes the wavelike propagation of electric and magnetic energy in a vacuum at the speed of light. After Maxwell's theoretical discovery/invention of electromagnetic radiation, that radiation became an object for physical research, and most famously Hertz's which culminated in confirmation of Maxwell's theory.
That's entirely consistent with the OP's suggestion is non-physical up to Maxwell's conceptual apparatus suggested its existence. — MetaphysicsNow

But in the end, Newton was right.

Perhaps a metaphysical definition would be that an event or object is physical if and only if it has a spatiotemporal location within some reference frame. — MetaphysicsNow

Some theories of mind claim that space-time only exists as a mental construction to help us make sense of the world. In this sense, the mind would be the only thing that gives rise to a spatiotemporal location. In this sense, the mind would be physical and everything else non-physical.

I really don't get the point of this debate. What is non-physical and what is physical? Who cares? What point does one hope to make when one finds that the universe is one or the other? How will that differ from the other's position?

To say that what is physical vs. non-physical is what is explained vs. what isn't is just referring to our own ignorance. There are physical things that have been explained and physical things that haven't been. To use these terms is just making things more confusing because it is a false dichotomy.