The project of how to reconcile our commonsense view of the world with how the sciences and philosophy seem to be telling us the world actually is, has been an obsession of mine for some time. To the detriment of my more terrestrial projects, I can’t stop thinking about (among other things) qualia, free will, metaethics, ontology of numbers and causality.
It is a characteristic of all these issues that they seem to present problems for what we might loosely call a physicalist or materialist or naturalistic or reductionist worldview. At its best, this kind of worldview does not imply a cartoon view that physics is the end of the story for human knowledge (though some, such as Alex Rosenberg, go that far), but rather an insistence that we keep our basic ontology (our catalogue of non-reducible things) to a minimum (especially ruling out fundamentally mental entities). WvO Quine famously identified the naturalist/physicalist/materialist/reductionist impulse as an aesthetic “taste for desert landscapes.” But that is a much larger can of worms, and I am not sufficiently confident in my opinions to open the whole thing just yet.
The problem of qualia is a problem for physicalist theories because it seems to imply that there must be facts about the world that refer directly to some sort of mental or subjective states. Various thought experiments can bring this problem into clearer focus; my favorite is Frank Jackson’s “Mary’s Room” thought experiment (great for thinking about when you get stuck in a queue). This SEP article is a fantastic summary of that thought experiment, as well as related ones. I want to present one of the standard solutions to Mary’s Room, which I think is rather elegant and decisive. But first, here is my brief summary of Mary’s Room (if you’re familiar, you can skip the next four paragraphs).
Mary is a genius neuroscientist. She knows everything there is to know empirically about how the mind and brain work, and in particular she exhaustively knows every single scientific fact that bears on color vision: optics, how the retina works, how the retina’s signals get processed in the brain, et cetera.
However, Mary has had an unusual upbringing. Raised by philosophers (a sketchy proposition in the best of times), she has been kept in a monochrome room for her entire life and has never seen primary colors — never seen a red rose, or a green leaf, or a blue sky. (Nitpicky readers will notice that this would be actually pretty hard to accomplish — for one thing, she would have to have her skin painted monochrome, never look at a bright light through her closed eyelids and see the red color that results, never dream in color... but never mind. This! Is!! PHILOSOPHY!!!)
Eventually, her philosophical zookeepers take a day off from heroically pushing obese people off bridges, and they take her out of her monochrome cage. She comes out into the world and sees a dandelion for the first time, saying “Wow, so that’s what yellow looks like! Cool!” You can imagine all her other epiphanies for yourself.
The gotcha being that she appears to have learned something new — what it’s like to see yellow — on being released. But we stated that she already knew all the scientific facts! Therefore, there must be facts out there that are beyond the reach of science, even in principle — mental facts, or subjective facts, perhaps. Facts about what it is like to have certain experiences. That’s the idea, anyway.
Various solutions have been proposed to this itchy little problem of Mary’s Room. Some of them appeal to the nitpicky objections I mentioned above — would it actually be possible to prevent Mary from having color experiences? Does neuroscience actually allow that the Mary experiment could be carried out?
While these are all good points, it seems to me that they miss the main thrust of the thought experiment. Nitpicky objections usually do, by focusing on an aspect of the problem that is unrelated to the real meat of the issue.
Another approach to solving the problem is to wholesale deny the existence of qualia. This has been attempted by several philosophers, and also recently by a LessWronger, whose post partly spurred me to write this one.
In principle I think it’s a healthy impulse to try and deny that some mysterious phenomenon exists, and see whether you lose any explanatory power. That approach can be applied productively to many problems, such as personal identity.
On the other hand, denying qualia still seems to leave me in the same state of bemused confusion that I was before. I still end up looking at a red traffic light and saying to myself, “That’s weird.” And the strategy looks kind of desperate — the moment phenomenon X creates a problem for physicalism, you deny phenomenon X altogether? Really?
One response to this among qualia-deniers is to appeal to the idea that intuitions are (very) fallible. Yes, this is true, but intuitions still provide prima facie reasons to believe in them. Being counterintuitive is not desirable, just acceptable. And ideally, if you tell me something wildly counterintuitive, it’d be nice if you explained exactly why it’s counterintuitive, instead of leaving it as a brute assertion that my intuition is wrong (here is a good example of a counterintuitive thesis that is explained beautifully).
One of the most popular approaches is to say that Mary is obtaining new knowledge, but that the knowledge is not about any new facts. This view can be termed the New Knowledge/Old Fact view.
I want to summarize this view... but I confess that I cannot make head nor tails of it. Here’s how the SEP summarizes it:
(1) Phenomenal character, e.g. phenomenal blueness, is a physical property of experiences.
(2) To gain knowledge of what it is like to have an experience of a particular phenomenal character requires the acquisition of phenomenal concepts of phenomenal character.
(3) What it is for an organism to acquire and possess a phenomenal concept can be fully described in broadly physical terms.
(4) A subject can acquire and possess phenomenal concepts only if it has or has had experiences of the relevant phenomenal kind.
(5) After release Mary gains knowledge about phenomenal characters under phenomenal concepts.
Well, I am just an amateur philosopher, so it’s quite plausible that my trouble in understanding this view is a function of my own ignorance of the correct subtle concepts. But this seems to be saying that the perceived blueness of blue is a “physical property” of an experience. A physical property of an experience?! Um... that does NOT sound right at all; in fact, it seems more confusing than the original problem. But again, I am probably not doing justice to this view; if you know an alternative way of explaining it, I’d be interested to hear it.
The solution that seems to me to really solve the problem on a gut level is called the “Acquaintance Hypothesis” and is associated with Michael Tye, among others — see his article here. I am less interested in getting all the definitions and necessary and sufficient conditions right, than I am in getting rid of the intuitive problem. So here is the general picture.
Mary does indeed learn something when she leaves the room. But what she learns is not propositional knowledge that can be stated in words. Rather, Mary becomes acquainted with brain states/mind states she has not occupied before. Obviously, her education in the neuroscience of color vision was not an education in learning to occupy new brain states — hence the radical disconnect between her education and her experience of seeing the blue sky.
Her new acquaintance with the redness of red now allows her to do other things, such as remembering what red looks like (by stimulating the same patterns of neural firing that corresponded to seeing red) and recognizing red when she sees it, and deciding whether red is her favorite color.
Similarly, you will never be acquainted with what it’s like to be a bat, but that’s just because you can’t occupy a bat’s brain state. It’s not because there’s some fact you don’t know about the universe.
I don’t know about you, but this satisfies me completely. After I hear this explanation, I look at a red traffic light and it doesn’t feel like there’s any mystery left over. One might draw a parallel between this and the mirror paradox: regardless of whether you can fully explain the geometry behind the mirror paradox, it just intuitively goes away when you get really close to the mirror and see each and every point being reflected in the same manner.
Now that we have this picture, we can see our way (albeit speculatively) towards how Mary might have acquired, via her book-learning, acquaintance with the redness of red. One way would be for her to perform some sort of meditations or mental exercises designed to guide her brain state toward the one(s) that correspond(s) to the color red. I have some doubts that this is really feasible, but its unfeasibility seems like a contingent fact about human brains, rather than bearing strongly on the problem of qualia.
Granted, this doesn’t solve every interesting problem about consciousness. One might still wonder about things like whether sufficiently advanced silicon-based robots, or Martians, or simulations of conscious creatures, could have qualia — and about whether they could be the same as ours (“yes on all counts” is my instinct). A nice discussion of such issues can be found here, in the SEP’s article on functionalism in philosophy of mind (as an aside, the SEP is a really, really good resource).
But leaving these other problems aside, I think I am ready to stop interrogating poor Mary and let her go on her merry way.