I have asserted many times here that physicalism as degraded into an undecidable question, and I would like to see how strong my understanding is.

It seems to me that whenever we approach the boundary of what should be considered physical, it retreats, without those insistent on physicalism ever having to admit any new limitation on what the new boundaries are.

We accepted that there is an absolute limitation on how well we can apply any physical law. And we declared that physics... Previous generations would have declare that mysticism (and quite a few since, have, actually, to the resounding dismissive moans of the literati.)

If an angel came up to someone and demonstrated his powers, a modern man is just as likely to assume they are some kind of advanced alien, rather than an angel. Or we will anthropologically and psychologically explain why they are the 'cause' of the mythology of angels, like in Arthur Clarkes "Childhood's End."

So, is there something that we could imagine having no physical explanation? Is physical well-defined enough to even have boundaries? If not, why ask questions about it?

Direct violations of existing paradigms don't count. We all know what happens when you break a physical law -- the law changes. What is really physically impossible (for you)?

  • Classical trap -> having technology does not mean understanding it, understanding it does not mean being able to create it. Difference between advanced alien and Angel is simple. Advanced alien is >advancing< through universe (getting new technologies and losing old ones) while Angel in common sense should be close to the complete picture of reality >thus< having no advances in simple sense. So the difference between angel and alien is difference between human and god. In their overall scope. They are similar yes, but what isn't?
    – Asphir Dom
    Nov 10, 2014 at 18:39
  • Right, so if you already accept the non-physical, you need no boundary around the physical. And if you do not accept the non-physical, you do not need a boundary around the physical. To me this is just another way of saying there is no question, just meaningless bias. What is the contribution?
    – user9166
    Nov 10, 2014 at 19:25
  • The physical is, trivially, what is studied by physics. The real question then is: what is actually studied by physics? This question is a lot easier to answer.
    – user132181
    Nov 10, 2014 at 20:21
  • So before anyone studied it, there was nothing physical? Your real name isn't Berkeley by any chance...
    – user9166
    Nov 10, 2014 at 21:09
  • @jobermark well yes I guess that's true: If physics is what we study, then it's an excercise in finding the "unknown unknowns". Before physics was studied, basic physics now would have been considered witchcraft or magic. It's still the case in a way. eg. Einstein predicted entangled photons (2 x photons which act the same way regardless of their location) and thought it odd so he called it "spooky interaction". It's since been demonsstrated. Nov 11, 2014 at 10:00

4 Answers 4


You're right, defining the physical properly is not an easy task.

There are two types of approaches: you can start a priori by assuming some defining characterisics -- among the various propositions, being located in space-time, having only objective properties independent from the mental, being structural or amenable to mathematical description, being constituted by ponctual entities...

The risk with this approach is ending up assuming that what physicists study is not physical after all. Many past intuitions on the physical are now known to be false (fundamental particles are not perfectly localised or impenetrable, their evolution is not strictly predictable, ...).

Or you can define the physical a posteriori: the physical is whatever physicists say it is, or whatever an ideal physics would say it is. The problem is: in the first case, your conception will be superseded as soon as new theories are discovered. In the second case, your conception might render physicalism vacuous. Of course everything is physical if "physical" is everything that is addressed by an ideal "theory of everything". This conception is not very informative. Or perhaps you have to say more about what theorising is about and what is admissible in physics (then you introduce some a priori characterisics). I suppose the argument you develop in your question is directed against this brand of physicalism, which seems not far from a vacuous position.

Although no approach is devoid of difficulties, there are arguments on each side and attempts to overcome these difficulties. You'll find an interesting, open access book chapter on the topic (from which I took my inspiration) for more detail and counterarguments on each sides: http://www.philipgoffphilosophy.com/publications.html (chapter 3)

  • These directions both set a minimum and not a maximum -- i.e. a basis and not a boundary. Many people seem convinced 'everything is physical' in a way that is not just a definition of 'everything', so neither of these can be such a person's operational definition of 'physical'.
    – user9166
    Nov 10, 2014 at 17:42
  • I edited my answer before I saw your comment. I agree for a posteriori approaches, not for a priori, which clearly set a boundary (e.g. being localised). Nov 10, 2014 at 17:57
  • But fields are not localised, and neither are Schroedinger distributions. So we have moved on from there, either at Maxwell or at Copenhagen. And we decided that was just fine. Same for point particles, etc. The only thing left is 'independent from the mental'. But no measurement or observation can be independent of eventually becoming mental, or we would not be observing it. So, if these are boundaries, they get crossed.
    – user9166
    Nov 10, 2014 at 18:18
  • I guess I skipped over mathematizability. But I reject that as a criterion for physicality, because I think we find math to predict things, we do not just happen to notice that we have math that predicts things. And if we didn't find any, we would not think "Oh, that must not be physical" we would think "Gee, we're stupid."
    – user9166
    Nov 10, 2014 at 23:59
  • I agree for localisation of fields (that was one of my point). One important aspect is: do not expect physicalism to be an empirical position, it's a pure metaphysical one. Nov 11, 2014 at 0:20

I think physicalism is most parsimoniously understood as an alternative to a model where there is a fundamental intelligence of some sort. For example, it rejects both the mental sphere of Cartesian dualism and the claim that reality is a dream of Vishnu.

In particular, this means that things are fundamentally composed of simple components that interact with each other via mathematical rules rather than social ones.

Now, one can object and say that one can imagine an entire continuum from simple equations based off of a tiny number of local states through simple probability distributions and then complex contingent ones based on sizable numbers of variables to something indistinguishable from thoughts of intelligent beings. Indeed! But the physicalist is committed to a vague statement of nothing going too far up that hierarchy--if it seems like it does, the physicalist is committed to the idea that it is composed of simpler parts with simpler interactions.

Exactly where that boundary lies is not, at present, all that important, as we haven't demonstrated that there is anything whose most fundamental behavior is terribly complex. (All sorts of emergent behaviors are terribly complex, of course.)

  • Comments are not for extended discussion; this conversation has been moved to chat.
    – stoicfury
    Nov 14, 2014 at 3:06
  • @stoicfury - It would be nice if we got the option a little sooner to do the move so you didn't have to keep doing it manually.
    – Rex Kerr
    Nov 14, 2014 at 4:45
  • I KNOW right? It gets auto-flagged at 20 comments, then I can one-click "move comments to chat" but then I have to delete every comment by hand, which is sort of like playing minesweeper with the little red x right next to the edit link. 406 deletions and counting...
    – stoicfury
    Nov 14, 2014 at 18:01

The transition from the common use of "materialism" to "physicalism" represents a recognition that the boundaries of the former are too narrow to accommodate what is now accepted about the nature of the world. I don't see a good reason to think that it is impossible that we cannot have a similar transition from physicalism to some x-alism if we were to conclude that there are some non-physical things that are none the less real (I don't know of any such things, but 17th century scientists/philosophers didn't now about quantum fields either).

Materialism, especially when differentiated from physicalism, tends to connote the idea that all that there is is matter moving around. Nowadays we consider various kinds of non-matter stuff -- energy, momentum, quantum fields... as being real. These non-material things are sufficiently different from (the conception of) "matter" as used by the early materialists and thus a new term is required. I can't rule out the possibility that in the future there will be some other kind of stuff, sufficiently different from what we currently accept lives under the term physical, that we'll again need to construct a new category. Of course I can't imagine what such stuff would be. Just poking around on the web I've found the mathematical universe hypothesis by Max Tegmark -- which has in it the idea that mathematics is "really real". If that hypothesis were to pan out, then one might reasonably say that physcialism missed the mark. There are probably other ways that one could immesh the laws of physics, or even mathematics itself, in with the the structure of the universe such that it would not be precise to describe these ontologies as being strictly physical.


This is a stronger version of @Dave's answer. It is given elsewhere, but it convinces me on this issue. There is a way to strip 'physics' off of this position that maintains the position, and that is to retreat to a weaker, but adequate position. Dave did not capture the position, but I buy this:


What I was looking for (had I known) is the decoding of physicalism as reductivist monism, as opposed to a bias against any specific wasteful trend, or an attachment to actual physics as a basis for judging acceptable notions.

Sorry if, in retrospect that makes the question quite badly put.

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