Spurred by conversations a few weeks ago, I’ve been thinking about physicalism, the stance that everything is physical, that the physical facts fix all the facts. A long popular attack against this view has been to argue that it’s incoherent, since we can’t give a solid definition of what “physical” means. And so physicalism seems to be built on a foundation on shifting sands. This is actually something I’ve struggled with myself.
On the one hand, defining the physical doesn’t seem that hard. Physicists don’t seem to have much trouble knowing what to study. Physics is usually described as the study of matter and related concepts such as energy, forces, fields, and spacetime.
But it’s often pointed out that the earliest proponents of the materialistic philosophy argued that everything was just atoms and void, with our everyday experiences coming from the motions and interactions of those atoms. It was in the 1800s when the existence of the other concepts started to get fleshed out.
It could be argued that those concepts are just the details of accounting for the motions and interactions Democritus was originally talking about. But it feels like more than that, particularly since matter at the most fundamental level currently accessible, quantum fields, seems far less concrete than what Democritus and Epicurus had in mind.
This leads to Hempel’s dilemma (presented by Carl Hempel in 1969), which asks if physicalism is about what physics has currently established. If so, then since everyone understands that current physics is incomplete, physicalism is wrong. Or if physicalism is based on some hypothetical future physics that is complete, then it seems vacuous, since no one know what that ideal physics might be.
Hempel gets at a core fact about all scientific knowledge; that it’s provisional, subject to change on future evidence, something that seems inevitable given the problem of induction that David Hume identified. Although I don’t take Hempel’s dilemma as a defeater of physicalism, but more an insight that the ontology of the view isn’t static, but something that is always changing and shifting. In my view, it should be seen as a strength, not a weakness. Don’t we want our ontologies to update as we learn more?
But it does highlight that the definition is tricky. Daniel Stoljar, in the SEP article on physicalism, covers a number of other strategies in trying to define “physical.” An interesting one is the Via Negativa, which focuses on what the physical is not. The example given is that it’s not anything irreducibly mental.
I like this approach because it gets at the real heart of the matter. If there’s anything that could kill physicalism as an outlook, it would be irrefutable evidence of some aspect of the mental being fundamental. Although Stoljar points out that there are other concepts generally taken to be non-physical, such as the élan vital.
Another approach which resonates with me as a structural realist is to define the physical in terms of structure. My way of describing it is to say that the physical is whatever is part of the structure and regularities of the objective world. That seems to rule out putative platonic objects and non-physical phenomenal structures, but include everything we normally think of as physical. Although I’m sure someone could come up with a concept that would frustrate it.
The one that might be the closest to truth is the idea that physicalism is an attitudinal stance. Stoljar discusses a version of this as taking one’s ontology from what physical theories describe. This is a bit narrow and he points out the obvious issues with it. Among them that it still seems vulnerable to Hempel.
But a better more general one might be an attitude, an expectation, that for whatever phenomena we are faced with, there is, at least in principle, an understandable explanation, one in terms of structure and regularities (laws). We see this stance at work with dark energy and dark matter. There’s no discussion about whether these are supernatural or occult phenomena. They are approached with the expectation that some kind of mechanistic explanation is possible.
A physicalist just applies that attitude to everything. Even if faced with something that might initially seem non-physical, the attitude that there is an understandable explanation underneath will generally exist. This seems to make physicalism similar to methodological naturalism, although the scope is more than just standard scientific investigations.
(There are people who make distinctions between physicalism and naturalism. For instance, David Chalmers consider himself a naturalistic dualist, so he seems to see himself in the naturalist camp but not the physicalist one. However, given that the etymology of “physics” is the Greek word for nature, and the etymology of “nature” the Latin word for physics, it seems like any distinction would be pretty subtle.)
This attitudinal way of looking at it may get at what’s really going on with a lot of these various metaphysical views. Physicalism is the attitude of everything being understandable, while other views like panpsychism and idealism seem more poetic and artistic in nature, more about seeking connection in reality rather than trying to understand and manipulate it.
Which raises the interesting possibility that there may be value in learning to put on “the glasses” of other views, to see the world through each of their filters, even if only for particular purposes, maybe for no other reason than to ensure our metaphysical biases aren’t acting as blinders, cutting us off from other possibilities.
In the end, for me, predictive success remains the best arbiter of reality. But the path to that success often requires unconventional thinking.
What do you think? Am I overlooking some of physicalism’s problems? Or its strengths? Or being too ecumenical in my closing?
SelfAwarePatterns 
I like the topic but some of the discussion … not so much. Re “This leads to Hempel’s dilemma (presented by Carl Hempel in 1969), which asks if physicalism is about what physics has currently established. If so, then since everyone understands that current physics is incomplete, physicalism is wrong. Or if physicalism is based on some hypothetically future physics that is complete, then it seems vacuous, since no one know what that ideal physics might be.”
No physical theory is ever complete, nor can it be. This hasn’t been proven as it has for arithmetic systems, but I think it is obvious, so the claim that physicalism is incomplete is specious.
Re “But it feels like more than that, particularly since matter at the most fundamental levels currently accessible, quantum fields, seems far less concrete than what Democritus and Epicurus had in mind.”
So? The founders of a theory rarely, if ever, have complete knowledge. One of the characteristics of a high quality theory is that it allows for future discovers. So, “all matter is made of atoms,” does that hold up? Well, neutron stars are not, yada, yada, yada, but Democritus and Epicurus were talking about ordinary matter and that claim holds up quite nicely.
Some modern theories say that, in the line of “it’s turtles all the way down,” that the universe is infinite whether you go outward or inward. If that is so then we should expect more and more complexity to be revealed as time goes on, but … So, what? At various levels we lose contact with the finer points. Cam you feel single atoms or molecules colliding with your skin? No, too small. There are galaxies colliding with one another, should we worry? No, too far away.
Our existence is withing a small sphere and the rules we make up from observations within that small sphere only need apply there. But, of course, when we check if the rules hold far, far away, we are not shocked to find they do (mostly). This suggests some underlying structural supports for those behaviors and existences … and as scientists we use what we observe as guides, not absolute truths. Sometimes philosophers cannot seem to know the difference.
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There are people who see Hempel as a devastating problem for physicalism, so I felt like I needed to at least mention it. And it does knock off simple naive attempts at defining the view and drive us to look at what might be more fundamental to it.
Turtles all the way down seems like more of a metaphysical view than a scientific one. If reality is fundamentally continuous, as in general relativity, then it might be infinite all the way down. Although the Planck scale seems like a barrier. Brian Cox recently noted that to probe scales smaller than Planck takes so much energy you end up creating a black hole. Which seems to put up a barrier to us going smaller. Although who knows what future experimentalists might come up with.
Philosophers do seem preoccupied with ultimate existence. The thing is, if the most fundamental scientific theories of today don’t accord with your view of ultimate reality, you can always hold out for a more fundamental theory that will. That’s one of the problems with metaphysical theories of ultimate reality; they’re fundamentally untestable.
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Re “Brian Cox recently noted that to probe scales smaller than Planck takes so much energy you end up creating a black hole.”
Look at how much energy it took to examine the insides of nuclei–far too great for the people at the time … but … sounds like just another energy barrier and I am hesitant to accept calculations based upon general relativity when it breaks down so often.
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Good point.
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It sounds like you’re describing physicalism as reductionism, which is probably the most popular form, though apparently there are non reductive physicalists. I’m not sure if I’ve ever talked to anybody who identified as such, though it seems like such a view is implied in supervenience
—Physicalism is the attitude of everything being understandable, while other views like panpsychism and idealism seem more poetic and artistic in nature, more about seeking connection in reality rather than trying to understand and manipulate it.
Idealists and panpsychists aren’t generally interested in making up poetic mysteries, though I can see why you might think that from reading my posts.
I’m curious why you think believing reality consists in the enduring structures of scientific theories is not mathematical Platonism. Aren’t these structures things like the standard model (ie equations, math?) Or were you thinking of something else?
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It is reductionist. Can’t say I know a whole lot about non-reductive physicalist views. I do know about Chalmers’ type-B materialism, but that’s just an argument that the reduction can only be a posteriori rather than a priori. Outright non-reductive physicalism seems like it would be a strange beast. But I do know they exist.
On idealism and panpsychism, that’s what I get for trying to describe views I don’t hold. How would you characterize the idealist attitude? Or do you think that’s not a valid way of looking at it?
From what I’ve read of mathematical platonism, it’s the view that abstract objects exist outside of space and time with no spatiotemporal extent or with no causal effects. I currently lean non-factualist about whether those exist. For physicalism, it seems like we’re talking about structures that are part of the world and do have causal efficacy. Am I overlooking something that makes the views more alike than I’m thinking?
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Maybe that phrase “non-reductive physicalism” is unpopular? Apparently some functionalist views are considered “non-reductive physicalist”, but it gets complicated. I wouldn’t be surprised if there are people out there who actually do believe in some form of non-reductive physicalism without realizing it. It does seem to be an uncommon label, at least lately.
As for idealism/panpsychism…these are hard to characterize as a group. Maybe mind is fundamental or primary.
I guess I assumed ontic structural realists would have to be mathematical platonists. What sort of structures survive theory changes and also have causal efficacy? Can you give me an example?
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Hadn’t heard that before for functionalism. Most of the stuff I’ve read has it firmly within the reductive physicalist framework. But it wouldn’t surprise me if someone has that take.
On idealism/panpsychism, right, I wouldn’t ask you to do it for panpsychism since that’s not your view. And mind is primary certainly matches my understanding of idealism. Thanks. I guess I’m asking how you see it changing the way you view or interact with the world. Or does it?
“What sort of structures survive theory changes and also have causal efficacy? Can you give me an example?”
The best examples might be Newton’s structures. You can see it in the equations between his theory of gravitation and general relativity; all his variables are present plus more for high velocity and high energy situations. The same is true for classical mechanics and quantum mechanics, particularly if you look at the Hamilton-Jacobi equation and compare it to Schrὅndinger’s. (Sorry, I don’t have the LaTex skills to show them here.)
But even Ptolemy’s geocentric structures can reportedly be seen as preserved in Copernicus’. They just have a much smaller scope of usefulness. It’s the interpretation, the story, that is radically different.
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“An interesting one is the Via Negativa, which focuses on what the physical is not. The example given is that it’s not anything irreducibly mental”.
Wouldn’t that mean also that whatever is “mental” is not “physical” and thus beyond the bounds of physicalism?
A comprehensive theory should explain both, so your attitude of looking for an understandable explanation makes sense.
I’m still not a fan of IIT but I think that likely that mind and consciousness are tied to information. Consciousness is a form of biological information in the brain that emerges from the secondary order of the brain’s chaotic processes. Information itself has a dual nature just as we perceive body/brain and mind to have. It exists in the order of something physical but stands also apart from the physical realization.
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“Wouldn’t that mean also that whatever is “mental” is not “physical” and thus beyond the bounds of physicalism?”
It would, if it was irreducible to physics. I think at that point we could say that physicalism was in trouble, at least in its most common forms.
I’m with you on information. And I don’t think IIT has a monopoly on information. It seems like a central part of every cognitive theory of consciousness. (And of cognition for that matter.)
Although I wonder if you have something like Chalmers’ double aspect theory of information in mind.
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Actually I really like that Chalmers quote.
Basically I agree with it, but I would like more bridging of the gap between physical and phenomenal.
At this point, I am thinking consciousness is secondary emergent order that expresses in vertexes, travelling waves, and possibly other geometric patterns in brain firing patterns. The patterns can feed back into themselves expanding and morph into new patterns. These morphing patterns are the raw material of consciousness that are brought together in extra dimensions (of undetermined sort, possibly information based) that can aggregate patterns from different parts of the brain and from different times the near present and past.
In this scenario, consciousness is like the messages contained in the brain patterns. Or, another way, the patterns are the physical substrate of the message. Understand by “message,” I am not implying a homunculus that needs to exist to understand it. We understand the patterns possibly simply because we are feeling our own neurons firing.
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From the perspective of my Cognitive Behavioural mindset, this looks like a problem emerging from human psychology, rooted in our limited sensorium. But, I’m not a physiciist.
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Could be. The dividing line between our psychology and the world seems like it can always be a tricky thing. Which is why I always fall back to depending the predictability of a theory. However we think of the boundary, it seems like the theory either increases the accuracy of predicting future conscious experiences, or it doesn’t.
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Nice essay Mike. This may not be germane to the points you are making but sometimes I think we sometimes dwell a little too much on labels. Labels are a little like maps—they are not the territory but help describe the territory. A highway map, if it’s done right, tells the truth and a weather map can also tell the truth from another perspective. But neither describes the territory from (as Hilary Putnam puts it) God’s eye point of view. I’m happy with the idea that we live in one world—and we seek to understand the truth about it from various perspectives. I think the ancient philosopher, Xenophanes got it right: “
“Truly the gods have not from the beginning revealed all things to mortals, but by long seeking, mortals discover what is better. As for certain truth, no man has known it, Nor will he know it. Even if a man should chance to speak the most complete truth, yet he himself would not know it. All is a woven web of guesses.”
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Thanks Matti. I definitely agree with that quote for metaphysical beliefs.
The labels often put people in different camps. And often the exchanges between those camps end up looking like butter-side-up vs butter-side-down type clashes. Jacy Reese Anthis called it “intuition jousting,” where people are just yelling at each other from different intuitive beliefs.
It can all be in fun as long as we don’t take it too seriously. But too many seem unable to resist getting carried away.
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