MORE MIND-BRAIN SUPERVENIENCE

My argument about mind-brain supervenience set off a huge discussion in the comments. It's times like this that I feel like I really learn something from blogging.

One thing is that I'm more and more convinced of my original claim, that is, of the necessity of agnosticism about mind-brain supervenience. With all due respect to my interlocutors, they're somewhat at a loss here. Either they re-assert physicalist tenets as dogmas, or they attack straw men while half-conceding the central claim.

But I also realize that my claim and the argument for it are more difficult to understand than I expected. Let me try to deal with some of the sources of confusion.

"Faith," induction, and Hume vs. Popper. A red herring in the discussion has been my occasional references to "faith."

I developed a somewhat idiosyncratic usage of this word in a previous post, "On Faith." Faith as I use the term is, to begin with, a belief-without-proof in the converse of two subversive possible views: skepticism-about-induction and solipsism. Induction skepticism and solipsism are positions that no one believes, but which (I claim) cannot be rationally refuted.

The idea of skepticism about induction comes from Hume's An Enquiry Concerning Human Understanding. As Wikipedia explains:

David Hume framed the problem [of induction]... Among his arguments, Hume asserted there is no logical necessity that the future will resemble the past. Justifying induction on the grounds that it has worked in the past, then, begs the question. It is using inductive reasoning to justify induction, and as such is a circular argument... By Hume's arguments, there also is no strictly logical basis for belief in the Principle of the Uniformity of Nature. Notably, Hume's stated position on the issue was that instead of unproductive radical skepticism about everything, he actually was advocating a practical skepticism based on common sense, where the inevitability of induction is accepted (but not explained). Hume noted that someone who insisted on sound deductive justifications for everything would starve to death, in that they would not, for example, assume that based on previous observations of, e.g., what time of year to plant seeds, or who has bread for sale, even that bread previously nourished them and others, that these inductions would likely continue to hold true...

My argument in favor of "faith" is a response (of sorts) to Hume's critique of induction. We all hold (I argue) a belief-- or "meta-belief"-- that there are patterns in the world. This meta-belief undergirds all induction. It itself cannot be justified, or even clearly stated. (What are "patterns?"). Yet we cannot-- we simply do not have the mental capacity to-- reject it. I use the term "faith" to describe this meta-belief because I see parallels between it and two other beliefs-- the belief that there are other people, and the belief in God-- which seem similarly unprovable and impossible even to state satisfactorily (what is a "person?" what is "God?") yet which are also universal or near-universal. (One can argue about how widespread, or how genuine, atheism is...)

Another response to Hume was offered by Karl Popper, in "The Problem of Induction" (1953). Popper actually denies that we use induction even in practice-- it is, he says, "a kind of optical illusion"-- but rather, we are continually framing hypotheses, each of which leads to predictions, and we accept these hypotheses as "conjectural knowledge" until they are falsified. A point that is given great emphasis is that to be scientific, a hypothesis must be falsifiable. We must know exactly what a counter-example would look like, and be ready to abandon the hypothesis if we see one.

Now, while I think Popper's argument is an admirable contribution, and in particular a useful way to distinguish scientific from un-scientific hypotheses, I don't think, for reasons that go beyond the scope of this post, that Popper quite succeeds in solving Hume's problem. I think that "faith"-- the meta-belief in patterns-- is still necessary. However, my argument for agnosticism about mind-brain supervenience is independent of the issue of "faith." It is Popperian. We do not know what a counter-example to mind-brain supervenience would look like; therefore the hypothesis is un-falsifiable and illegitimate, and we must relinquish knowledge-claims about it.

Let me add, too, that the Humean critique of induction applies only to knowledge that is based on induction, mainly from sensory experience. I do accept subjective experience as a valid-- a "foundational"-- knowledge source, even if our reporting of that experience is, of course, imperfectly reliable.

Meta-induction and the motivation of physicalism. One response of physicalists to this argument is simply a dogmatic assertion of physicalist tenets. An e-mailer wrote: "I'd say that application of an epistemic falsifiability criterion on something like supervenience would not be appropriate. Supervenience is a means of setting the parameters of physicalism without metaphysical ghosts and spookies." Tom asserted that "in order for anything to have a cause and effect relationship it must be of the same system," i.e. the causal closure of the physical.

These are assertions rather than arguments and don't need refuting, but they raise the issue of why people embrace the physicalist dogma in the first place. I think the reason is a mis-application of induction. We have explained so much, the argument goes, within the physicalist parameters of the scientific method. So much that was once mysterious is now explained. Surely the natural sciences will eventually explain everything, conquer all the mysteries, will reduce everything to the building blocks of matter, energy and force!

We can easily see the flaw in this with the help of Karl Popper. What is the falsifiability-criterion of "science can explain everything in physicalist terms?" Suppose there is an unexplained phenomenon. Scientists try to explain it in physicalist terms. If they succeed, great, the physicalist hypothesis is vindicated! But if they fail, the physicalist hypothesis is not falsified or abandoned; scientists will keep looking for another physical explanation. It's "heads I win, tails we flip again." Since under no circumstances would scientists abandon the physicalist hypothesis, the physicalist hypothesis itself is un-falsifiable. It is the methodological assumption of the natural sciences, yet is itself unscientific.

Although it's easy to refute, the physicalist fallacy has deep roots in our culture and is very hard to destroy. Like a weed, you can rip it up again and again, but it keeps popping back up.

Science and intersubjectivity. Another type of response to my argument (particularly by Nato) was to insist that only "entities with testable properties" deserve consideration by science. This type of response actually concedes the central point, agnosticism about mind-brain supervenience. Maybe, it says, there are "tiny angels making the neurons fire," or whatever. But if these non-physical entities don't have testable properties, science has nothing to say about them.

Now, for the phrase, "testable properties," we must substitute "intersubjectively testable properties." My mind, after all, has plenty of properties that are quite evident to me: I enjoy (or suffer from, as the case may be) an endless stream of subjective experience. But this subjective experience is private. I can describe it to others, but often I don't, and even when I try to, the result is very imperfect. When I am confronted with any physicalist account of the operation of the mind which has implications for my subjective experience, I can always tell the scientist, "No, my subjective experience is inconsistent with your theory." But he can't see that for himself. Maybe we are misunderstanding each other, or maybe I am lying. It's not like a chemistry lab, where he can see the litmus paper turn red.

Agnosticism about mind-brain supervenience implies that non-supervenient minds, or non-supervenient aspects of minds, may or may not exist, but we cannot rule them out. The claim that every thought corresponds to some firing neuron might be true, but we can never prove it, nor even frame it as a Popperian-style falsifiable hypothesis and call it "conjectural knowledge." We must abandon it. Nato seems to accept this as an ontological claim, but argues that science can and ought to ignore these entities that are not intersubjectively testable, even if they might exist.

Well, yes. The methodological policy of science is to focus on that which is intersubjectively observable; and as the human condition happens to be such that all intersubjectivity is mediated through the physical world, science focuses on that. But that is a truth about science, not about the world. It doesn't follow that the physical world is all there is, or all that we need to know about.

Minds exist. We know from subjective experience that they exist and something about what they are. Minds matter. We know there is, at the least, some kind of interface between mind and body. The natural sciences can study that interface and teach us some useful things about the mind. Minds may, indeed, be supervenient on the physical world, but we do not know that they are. The supervenience of the mind on the brain is a claim that can be uncritically accepted as dogma, but cannot meet the Popperian standard of falsifiability.

If minds are, or may be, non-supervenient, or partially non-supervenient, on the physical world, they still matter. To simply exclude them, or aspects of them, from consideration on methodological grounds, will not do. The loss of the comforting intersubjectivity that comes from assuming a physicalist ontology is a price we'll have to pay.

This is where it gets interesting. The possibility of non-supervenient minds become a gateway to a richer ontology, because it is a license to take our mental experience more seriously. Platonism, with its Ideas of which the things we see in the world are only shadows, flickers to life as a renewed possibility...