Brandon Oto
11/5/08

The Long Arm of Physicalism

Self-professed qualia freak Frank Jackson has put forth the influential “Knowledge Argument” against physicalism, wherein he attempts to show that physical facts cannot be the only facts, and therefore that physicalism does not capture the entire extent of reality. I find his case to be interesting, elegantly-presented, and outrageously wrong—not just unconvincing but actually predicated upon an incoherent foundation—as well as revealing, in its wrongness, a key point of confusion within the ongoing physicalism debate. I will try to illustrate both of these ideas below.
To briefly reiterate Jackson’s case, the story so far: Mary is a brilliant scientist who has spent her entire life ensconced in a room where no colors are present except black and white. She spends her time learning the facts of the world, namely those regarding color vision, and most of all about the color red: what it consists of, its nature, its effects on the human eye, and so on. Indeed, she learns absolutely every physical fact about the color red, all without ever actually seeing it. Finally, one momentous day, she is allowed to come forth from the room, views an instance of red for the first time, and, it seems, must surely learn something new—this is what it’s like to see red! But as she already knew every physical fact, what she now learns must be some non-physical set of facts, ergo not all facts are physical.
Or not. The trouble is that what Jackson seems to mean by “physical facts” are only the most banal sort of facts: facts about the refractive properties of red, and the optical components that are sensitized to them in humans, and the neural activation undergone in its presence, and so forth. These are certainly physical facts, but it is absurd to claim that they are the only physical facts, and if it is remarked that those are what we generally think of as physical facts, or at least that they are the easiest example of physicality, then that is perfectly true but beside the point. It would be quite beyond me to communicate, in any direct way, the exact nature of a spinning top whirling around my desktop; the physics involved and the specific path it takes are highly complex and there is simply no good way to express them in English sentences. I would have to produce hundreds if not thousands such sentences, painstakingly explaining countless details about the top’s coordinates and vectors, and undoubtedly your ability to parse and combine them would be similarly poor. Nevertheless, there is nothing non-physical about the basic movement of a spinning top; it is simply the case that this particular type of physical data is poorly suited to being expressed via our current linguistic devices.
Likewise with the case of Mary, it is all very well to say that Mary learns “all the physical facts,” but in reality this would be next to impossible. The relevant physical facts don’t just include bland commentary on wavelengths and neurons, they also include the ones she supposedly learns upon leaving the room, such as certain truths about how red manifests in the visual field and what its mental associations are in humans. How can these be encoded into propositional sentences and printed in her textbook, then uploaded to the right sectors of her brain? Probably they can’t, but this does not make them magical or non-physical, it just makes them ineffable (and contingently so—perhaps better tools could communicate them more effectively). After all, if Jackson could express any one of this mysterious collection of novel facts in words, then I would happily say, “You’re right, she did just learn that—but what a terrible error! That’s a physical fact and she should have learned it in the room.” On the other hand, if by some means Mary does learn all physical facts in her room, then she learns nothing new when she leaves, because the subjective qualities of redness were available in her textbook, indeed occupying many chapters. She may confirm them, but that is not learning.
The obvious move by Jackson in response to this will be to say that I have recast physicalism to include everything imaginable, making the theory both true and trivial. “The physicalism I meant was this talk of neurons and so on,” he might say; “I don’t know what you mean by physical, but I’d sure like to hear it.” And indeed, the requirement to define what physical means seems a fair one if we are going to claim that all things are physical.
This is the most interesting juncture yet, because upon examination, what we mean by “physical” really is “everything that exists” or “everything that is real.” This becomes obvious when we see that there is nothing we can put on the table that a good scientist would not accept as physical, so long as it actually exists. If tomorrow new data comes forth showing beyond any doubt that humans have souls (somewhere above the large intestines), science will embrace the soul as a physical thing—as-yet unknown, mysterious, but certainly physical. The same goes for ghosts and superstrings and the Great Pumpkin; even if it turns out that ghosts live in another dimension and are invisible to cameras and serve an evil demon, that would simply become an exciting new branch of science. Mental events are no different. (Of course, good scientists might claim that something that cannot bear a certain degree of observation or falsification is not a valid subject for empirical study, but that is an epistemological constraint, not an ontological claim; they are not claiming it is not physical, merely that we cannot know anything about it.)
“Physical” merely means “real,” as contrasted with not-real, imaginary, or nonexistent. The confusion is when dualists or similar interlocutors try to introduce nonexistent new categories by simply negating the physical; Descartes’ soul is non-extended, non-material, etc. If the dualist can explain what his new substance actually is then the physicalist will call it a physical thing (at least a possible one—whether it actually exists would be an empirical matter). However, invariably the dualist simply claims it to be outside of the physical no matter how far the physical might stretch, and this is Jackson’s move. Whatever Mary might experience outside her room, he says, it must somehow be non-physical—never mind what it actually is. Wrong: it is physical; under identity theory it is a collection of brain events which for humans manifests a certain way; but even if her mental event was not a brain event but rather, say, a tiny window inside her optic nerve being opened by a mighty god, this would not make it somehow non-physical and mystical and extra-worldly, it would just mean that our scientific understanding of the process of vision is very inaccurate. “Physical” is not some category of reality, in which we store tables and chairs but nothing else; physical describes all of reality. This being the case, the assertion that a certain event is “non-physical” is either incoherent (the asserter simply doesn’t know what he’s talking about) or analytically false (since “non-physical” literally means “not real,” and nonphysical events are therefore a priori an impossibility).
Those who like to say “non-physical” similarly like to wave their hands on its details; “You can at least imagine something not part of this world,” they might say, and move on with their argument (in effect creating a deus ex machina they can disassociate from any inconvenient laws of reality). Well, no; if it is real, then it is the sort of physical we mean, and if it is not real, then you cannot use it in your argument.
In short, there is no real sense in saying that Mary learns non-physical facts when she leaves her room; she may have learned everything in the room (if our teaching methods are truly remarkable), or she may not have (if limited to today’s language and mental uptake), but either way the only coin at play is that of physical reality. Possibly this reality would be most easily conveyed in subjective or advanced ways like poetry or high-tech mind transfer, but for Jackson to suggest that this makes them non-physical is quite meaningless unless he can tell us what “non-physical” might positively refer to, whereupon we will promptly call it physical if it is real. 
If his thesis is simply that Mary learns more than these statements about waves and neurons could tell her, then that is true enough. Indeed, if his thesis is that the current understanding of the psyche is false and mental events are something other than brain events, this is a legitimate claim to make, but it is empirical and he has offered no evidence for his claim; for instance, he might say that mental events really are vibrations from passing unicorns, but this is would merely be an ordinary theory like any other in the annals of science, to go toe-to-toe with the theories involving neurons (and probably lose). The mere claim that mental events are other than physical is not just wrong, it is contentless; it is nothing more than an empty negation.