Thursday, October 8, 2020

Microphysics and philosophy of mind

Much (but not all) contemporary philosophy of mind is written as if microphysics were fundamental physics. But as far as I know, only on those interpretations of quantum mechanics that disallow indeterminacy as to the number of particles can microphysics be fundamental physics. The most prominent such interpretation is Bohmianism. On most other interpretations, the most we can say about the number of particles is that we are in a superposition between states with different numbers of particles. But reality has to have determinate numbers of fundamental entities. The picture of reality we get from both relativity theory and mainstream interpretations of quantum mechanics other than Bohmianism and its close cousins is that fundamental physical reality consists of global entities such as the spacetime manifold or the wavefunction of the universe rather than microscopic entities like particles. (I am attracted to a non-mainstream interpretation on which the fundamental physical entities may include mid-sized things like dogs and trees.)

Sometimes, pretending microphysics is fundamental physics is excusable. For certain discussions, it doesn’t matter what the fundamental physics is—the arguments work equally well for global and local fundamental entities. In other cases, all that matters is relative fundamentality. Thus, facts about chemistry might be held to be more fundamental relative to biology, and facts about microphysics might be fundamental relative to chemistry, even if the microphysics facts themselves are not fundamental simpliciter, being reducible, say, to facts about global fields.

But even when the arguments do not formally rely on fundamental physics being microphysics, it is risky in a field so reliant on intuition to let one’s intuitions be guided by acting as if fundamental physics were microphysics. And doing this is likely to mis-focus one’s critical attention, say focusing one more on the puzzle of why the functioning of various neurons produces a unified consciousness than on the puzzle of how the functioning of a handful of global entities results in the existence of billions of minded persons.


Martin Cooke said...


I wonder if those philosophers of mind are making any assumptions about fundamental physical reality, though, rather than simply observing the science. Whatever the fundamental nature of reality, we begin in the world of ordinary objects. This is where we think about anything. This is where the science is. And if you look at the scientific experiments, they tell us that the earth is round, that it goes round the sun, that individual electrons go through both slits, and so forth. Such things are much more certain than the theories about what is fundamental.

As for fundamental physical reality, perhaps there is an analogy with fictional creations, since this world is (probably) a creation. The fundamental fictional reality is not the whole book, nor the individual letters. The book can be corrected or revised; the letters of translations can be different. The fundamental reality is the main characters and the basic plot. So, I think you may well be on to something with your non-mainstream interpretation. But the properties of such ordinary objects are investigated by way of ordinary laboratory experiments.

Michael Gonzalez said...


Just the tiniest correction: The experiments do not tell us the electron goes through both slits. That's one possible interpretation of the situation, but we've replicated two-slit effects at the macroscopic scale just by incorporating an actual wave along which the object is traveling (very much like how de Broglie and Bohm thought about quantum objects). The macroscopic objects always pass through one slit or the other (of course), but the hydrodynamic effects guide each one in such a way that the wave's own interference gets translated as an interference pattern in how the objects eventually arrive at the screen.

More importantly, though, I think it is critical to distinguish what philosophers should do from what they often do do. Philosophers should be working on conceptual clarity, not just accepting whatever strings of words come out of the mouths of scientists. To take your approach, philosophers of mind would have to just accept things like the results of the Libet experiments, and then work on how we can live despite not really having free will. Hardly! They should criticize (as many rightly have) the deep conceptual confusions that permeate those experiments (e.g. that voluntary action is always preceded by individual acts of will, that there is anything it feels like to decide, that acting on an urge is anything like a paradigmatic case of voluntary action, that non-free subjects could report truthfully rather than just however their brains were wired to respond, etc.).

Besides, Martin, consider that the sciences often teach us about things like "what this organ does" or "what role this animal plays in its ecological niche" or "what is best for the health and wellbeing of this type of plant", none of which are within the conceptual reach of the vocabulary of microphysics. So, the reductionist dream is just misguided from the outset. Some things, for sure, are (at least partially) explained by appeal to their smaller components; but why think that most or all things are?

Let me add that I think agree that Pruss is likely onto something (heck, even a Bohmian view might include a fundamental object that is as big as space itself). But, it also seems quite clear to me that "minded creatures" are a subset (specifically, a language-using subset) of "animate, living creatures", and the reductionist needs to already back down in the face of mere life.

Martin Cooke said...


I think you are right about the important points you make. And that Alex is right about what the important question is. I had not noticed that way of looking at things before. I had noticed that puzzles about physical infinities are often answered (by those who like the standard set theory, as a foundation of mathematics) by observing that the puzzle just puts a constraint on what is physically possible; basically, the puzzle acts as a boundary condition on the equations of the global physics. But I have never before seen this way of looking at things in the philosophy of mind. It seems to make a lot of sense.

Regarding particles moving on waves in a fluid, the particles in question are moving in a vacuum when they individually go through the two slits. The obvious explanation would be such a fluid, were there not such a telling absence of corroborating evidence for it.

Michael Gonzalez said...


Fair enough, though I would think that the interference pattern is "corroborating evidence for it". Evidence is that which makes a view more likely true than it would have been without that evidence. So, if a Bohmian claimed there was this wave in addition to the particles, but the two-slit experiment didn't have the wave-type results, then the Bohmian would have less evidence for their view than they actually do have (since we do get the very results you'd expect given the fluid idea; indeed the very results we get at the macro scale by using a fluid).