As always, there's an interesting discussion going on over at Malcolm's blog, this time in the comments thread following this post on the "substance" of substance dualism (dualism is a philosophy of mind normally associated with René Descartes, who divided the universe into res cogitans and res extensa-- roughly, mental and physical phenomena). Malcolm and his interlocutor Bob Koepp have been going at it for several rounds now. My own take, as noted in a brief comment on Malcolm's site, is that dualism, as a vision of mind, is of no use for people in the field of AI. Artificial intelligence, which is undeniably improving though it is far, far from delivering to us anything remotely humanlike, bases its progress entirely on materialistic (or physicalist) theories of mind. Dualism, as Malcolm notes, sees the Cartesian res cogitans as immaterial and capable of subjective experience. As Malcolm remarks:
No, the way I have always understood this derisive use of language like "spookstuff" (and scornful and derisive it is) is that it is a reaction to the fact that the "substance" of substance dualists is never given any definition or description other than that it is "immaterial", and that it is capable of subjective experience. This is, I think, utterly unhelpful, and adds no explanatory leverage whatsoever. We are constantly told by dualists that it is somehow self-evident that "mere matter" can't possibly be the substrate of subjective experience (a claim that presumes an exhaustive understanding of what "mere" matter can and cannot do, which strikes me as astonishingly premature), yet we are never told by virtue of what, exactly, an otherwise indescribable non-physical mental "substance" is able to pull the trick off.
In his replies to Malcolm, Bob notes:
1. [W]e need to face up to the fact that the "substance", not only of dualists, but also of materialists, is pretty mysterious — some might even say it's spooky. We don't have a decent theory of material stuff and we don't have a decent theory of mental stuff. And lest anyone say, "But physics provides a decent theory of material stuff!", I can only say we don't even know why (or whether) gravitational fields are generated by matter.
2. Modern science has learned the trick of starting in the middle of things, working toward local, tentative solutions to problems without settling "foundational" issues.
Part of the problem, especially for dualists, may be the "substance/accidents" dichotomy, which to my mind is probably false. As things stand now, I see, especially from the dualist camp, a continued insistence on asking, "What is the substance that explains the accidents that scientists observe/deduce?" The question already assumes the substance/accidents dichotomy. Is this line of inquiry legitimate? If so, why?
While the question of the explanatory power of rival visions of mind (physicalist or dualist) is vitally important, I see the more practical question -- whether the dualistic conception of mind can help us make progress in fields like AI -- as a good gauge of dualism's viability, or lack thereof. If progress in AI continues (and we are undeniably creating machines that can solve increasingly complex problems) thanks to physicalist assumptions, I think the burden is on the dualist to explain why this progress is occurring. Simply dismissing the entire effort as "not being progress," as some dualists contend, is a cheap and lazy cop-out, in my opinion.
Regarding science starting "in medias res" -- I agree; science often does start in the middle. But with equal frequency, science moves beyond its starting points, both backwards toward fundamental considerations and forwards toward the realization of imagined realities; whereas dualism, like almost all the basic philosophical questions, seems to paddle around in circles. Progress in discovering the nature of mind won't occur through philosophical exchanges, I think, because nothing in philosophy is resolved forever, whereas specific questions in science often are resolved (e.g., How can we build a flying machine?). Even old philosophical points of view that appear to have been defeated can come back in the guise of some "neo-X" school, shored up with different arguments, but essentially propping up the old "paleo-X" view. The "anti-X" school can go through exactly the same process of death and rebirth in "neo-" form, with X and anti-X swatting the ball back and forth for eternity. Philosophy has more in common with the zigzag of ping-pong than the flowing linearity of archery.*
Technologically speaking, what we're moving toward is the creation of entities that may think and act in a manner we find totally human (or that may move beyond even the human threshold). Once we reach that point -- where it becomes impossible to distinguish machine behavior from human behavior -- we will be living the "zombie problem," wondering whether these machines should be considered beings with internal lives. But my contention is that, if we do manage to create machine entities of that complexity, dualists may as well admit the game is over: the functionalist wing of the physicalist view will have demonstrated that a true mind** can be created without once making reference to (or making use of) some other substance, whatever that substance might be. The zombie question will, of course, linger, but more for reasons of dualist stubbornness than anything else.
What dualists can't do, even now, is establish that other minds exist. To me, this makes it impossible for dualists even to make statements about mind in general. The radical subjectivity of qualia, which appears to be a dualistic axiom (and, to be fair, it's at least provisionally accepted by some materialists as well), prevents general conclusions about mind from being drawn. If your theory of mind is based on an idea that is little different from solipsism, you can't really expect such a ruthlessly internal worldview ever to aid progress in exploring what is essentially a practical, external matter. Why external? As I contended in my long-ago essay, I'm not convinced that first-person and third-person ontologies are separated by an unbridgeable gap. Science, that bastion of third-person ontology, is more likely than philosophy to provide greater insights into the nature of mind.***
*I'm not implying that the direction of scientific progress is linear. To the contrary, many of our leaps and bounds in science began as fortuitous accidents. Scientific progress includes many branchings, dotted lines, and dead ends. But at least it's progress.
**The dualist is trapped if he tries to argue that we simply cannot verify that a sophisticated machine is manifesting consciousness. Such an argument, taken literally, means the dualist is saying he doesn't know what consciousness is (you have to know what something is to be able to test for its presence, as when we test for HIV). If that's the case, then by the same token he can't tell me whether the person next to him is conscious or not. Does the dualist really want to be in such a position, unable even to say whether another person is conscious? He's there already, in my opinion, because his point of departure is a non-starter: the radical subjectivity of qualia.
***On a conciliatory note, I'll admit that there's nothing wrong with science and philosophy working hand in hand on this problem (in fact, a bit less acrimony and a bit more cooperation might actually be helpful!), but I still doubt that meaningful results will appear from philosophy's end.
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