…the argument goes like this: Physicalism claims that if you know all the physical facts that there are to know about people, then you know all the facts there are to know about them, period; for human beings are (says the physicalist) entirely physical. But now consider Mary, a master neuroscientist of the future. Mary has lived her entire life in a black and white room, and has never had any experiences of colors. Still, having studied all the relevant neuroscientific literature, she knows everything there is to know about the physics and physiology of color perception. Hence she knows, for example, everything there is to know about what goes on in someone’s brain when he sees a red object, everything there is to know about the surface reflectance properties of red objects, and so forth. Now imagine that she leaves her black and white room and sees a red object herself for the first time. Does she learn something new? Surely she does – she learns what it's like to see red. But then, physicalism is false. For though Mary knew all the physical facts about human perceptual experience before she left the room, she didn't know all the facts, since she learned something when she left the room. Hence there are facts about human nature, and in particular facts about conscious experience, that escape the physicalist story – namely facts about "qualia," the subjective features of a conscious experience in virtue of which there is "something it is like" to have that experience.
As always, Dr. Feser's post is well worth reading, so I will not go on discussing it per se. Instead I want to propose two brief considerations, which I hope to develop, in defense of qualia based on a "Mary's new knowledge" scenario.
First, let us imagine Mary is given only one day outside of her black and white laboratory world, and then must return for the rest of her life in that environment. If on Tuesday she has never seen a red object and on Wednesday she sees numerous red objects in the "real world," we already have a reason to believe in qualia, as Dr. Feser's summary of the argument above indicates. Yet I want to focus on Mary's cognitive condition on Thursday. If a physicalist denies Mary gained any new cognitive content (i.e. the quale of red) on Wednesday, would he go so far as to say her cognition was not at all altered on Thursday? For clearly something is different about Mary's cognition on Tuesday and on the post-red Thursday: she now has a memory of red objects, and that memory is the only thing she will have to her dying day to give content to anything she reads about "red" in her studies. The point is that the memory of what she saw during that red Wednesday will naturally insinuate itself every cognitive moment dealing with "red," and in a way significantly different from her cognition prior to that Wednesday.
The point is that if, according to physicalism, nothing was significantly different about Mary's cognition (viz. of redness) prior to seeing red objects and while seeing red objects, then why is her cognition manifestly different on Wednesday and afterwards? It must be granted that her cognition is different on Thursday, since the premise is precisely that Mary has a memory of red, which is a cognitive content she had no way of gaining prior to Wednesday. Mary could not have a memory of what does not exist and therefore her having memories of real redness indicates the reality of real redness as a conscious quale. If it is retorted that Mary's memory of red objects is no different from, much less superior to, her conception of it based on total physicalist knowledge prior to Wednesday, then the physicalist must grant that any conception of a reported experience is just as good as a memory of an actual encounter with it, an admission which shreds empirical science, and which anticipates a surprising connection between physicalism and its nemesis, dualism (esp. Cartesian), of which more presently.
Second, I think the Mary argument is too narrow and should be deployed as only one sliver of an entire category of arguments about consciousness, namely, the category of sensation as such. About a year and a half ago, while reading an essay by Mario Derksen, "Against the Skeptics: How Thomistic Realism Refutes Radical Skepticism", I was struck by his repeated allusions to the sense of touch as a, if not the, basis for epistemological realism. Derksen notes that the realism debate is too often shunted into debates about sight, which can easily be entangled in skeptical worries, whereas the sense of touch––the feeling of your buttocks on the chair right now, or the feeling of a coffee mug in your fingers, or the feel of your spectacles on the bridge of your nose, or the feeling of your forearms on the desk, and so on––of itself undermines skepticism, since the very notion of feeling intrinsically involves feeling what is felt. We would, in other words, have no conception of touch if we did not already intrinsically feel during the act of touch. If there is no qualic content in the act of touching, then nothing should alter in cognition when we are not touching and touching an ice cube. Visually, of course, nothing does change for us in terms of touch when we look at an ice cube but do not touch it, but that's the point: anti-qualia physicalism unfairly frames the debate about qualia in terms of sight, since this is for some reason easier to complicate than the intrinsic difference between, say, having shampoo in your eye or not.
The connection I want to make with Mary's cognition is this: suppose Mary were born totally blind but had learned her whole life what red 'looks' like, and then one day is granted restroed vision (by her unseen Alpha Centaurian keepers, of course)––it is manifest that her cognitive world would change in a radically qualitative way. Or imagine that she had been born deaf but had read her whole life what Beethoven's music 'sounds' like. When the Alpha Centaurians give her hearing and tickets to a Beethoven recital it is more than absurd to claim her consciousness would not be qualitatively altered. Now imagine she had been born with a rare condition of total numbness––and by total numbness, I mean she lacked even proprioception and the ability to feel her organs operating within her––but somehow she is taught by sight and sound what corduroy and what snow down the back of your shirt 'feel' like. Then one day the Alpha Centaurians give her normal nervous sensation. It is obvious that her consciousness would be qualitatively different after this operation. Finally, imagine Mary was born totally devoid of all sensory ability: no sight, sound, taste, touch, or smell. Yet somehow the Alpha Centaurians instruct her about how the world 'is' by way of directly sending electrochemical impulses to her brain. Then one fine day Mary is given all the normal senses. Yet, outrageously, according to the physicalist, nothing would change for her in terms of actual consciousness.
I want to emphasize two points from the above scenarios. First, physicalist arguments against qualia are parasitic on consciousness as a given. Refuting qualia in light of Mary's knowledge of red––a refutation I believe fails, anyway–– is like refuting the existence of trees as such since a certain species of tree was proven to be a large bush instead. Physicalists draw upon qualic consciousness all the time, even in their refutation of Mary's new knowledge, since they already grant she has visual consciousness of black and white, light and dark, etc. [NEW CONTENT SINCE FIRST POSTING: Thus it is very heartening to read in Howard Robinson's essay, cited in Dr. Feser's post, "Why Frank Shouldn't Have Jilted Mary," that his own assessment of Jackson's volto face towards physicalism rests on "his failure to appreciate the full force and generality of the argument" (The Case for Qualia, ed. Edmond Leo Wright, MIT Press, 2005, p. 240). Robinson elaborates:
The dialectical situation in which the knowledge argument is usually taken to be located is the following: it is accepted that physicalism gives an adequate account of non-conscious reality, which constitutes almost 100 percent of the universe, but struggles to accommodate certain features of mental life, namely the "what it's like" or qualia of certain conscious states. These latter constitute the "hard problem" for physicalism. The fact that they also constitute such a tiny part of the world is presented as a reason for thinking that they cannot plausibly be held to refute a unified physicalist account.
This presumption in favor of physicalism, based on the seemingly little that it fails to explain, would be a case of the fallacy of weighing versus measuring evidence, such as Hume commits in his argument against miracles from common testimony. The question of miracles depends not simply on the metaphysical possibility of their taking place, a possibility Hume has no way of forestalling, but also on the veridicality of miracles taken on a case by case basis. Merely because, say, healing by prayer is uncommonly witnessed (in terms of "evidentiary weight") does not entail that specific cases of such healing can be disbarred from the outset without their "evidentiary stature" being measured in its own right. (Indeed, if miracles happened more often than not they would eo ipso cease to be miracles!)
Likewise, merely because physicalism seems to cover so much of the universe––atoms, molecules, inanimate objects, etc.––, and thus boasts of the most evidentiary weight, this is no reason that the evidence for which it cannot account is to be disbarred. I take Robinson's point to be rather like a man caught red-handed in the town square with his hatchet sunk into his neighbor's skull arguing for his defense on the grounds that, since the overwhelmingly vast majority of human deaths occur without him or his hatchet being in the vicinity, therefore it stands to reason that he couldn't possibly have murdered his neighbor. The more he waves his bloody hatchet and hands around to show how irrelevant they are to "death itself" as a global reality, the more he incriminates himself by the very immediacy and specificity of his hatchet and hands. Precisely because the datum left unaccounted for by physicalism is itself involved in the evidentiary weight in physicalism's corner, it behooves the inquirer all the more to measure exactly why physicalism fails in such a cardinal way. Robinson explains:
I think that this [i.e. the dialectical bias described in the quotation above] constitutes a radical misunderstanding of the dialectical situation. What the argument really brings out is that only experience of the appropriate kind can reveal the qualitative, as opposed to purely formal and structural, features of the world. The kind of thing that Mary did not know, generalized from color vision to all the other sensible qualities, is essential to any contentful conception of the world, and physicalism without it would lack any empirical content. (my emphasis added)
Robinson's point is well taken, for, as he concludes on page 243, "if what the knowledge argument brings out is that our understanding of the physical world presupposes something which can be captured only in the special nature of experience, then … classical physicalism is broken-backed from the start." Without consciousness rich in qualia, there would be nothing of which observers could be conscious to explore the physical world. I don't know of any physicalists that claim rocks observe the world, and the reason is that rocks lack the very thing that would register there being a sensibly variegated 'world' to it, namely, qualitative consciousness.]
The second lesson is more counterintuitive and amounts to the paradox that anti-qualia physicalism terminates in Cartesianism. Recall the totally a-sensory Mary in my scenario above: she lacked all qualic conscisouness as such, since she lacked all sensory input as such, and yet the Alpha Centaurians were able, presumably, to teach her about the world by way of pure information, by way of pure thought. If Mary really gains nothing new by an embodied visual encounter with real redness, and if true knowledge of the world consists solely in physical facts about the 'naked', un-qualed world, then physicalism implies that human knowledge is totally independent of qualic sensory input, which is of course precisely the point of Descartes's positing of human nature as a res cogitans.