Can You See the Insides of Your Eyelids?

Visitors to The Splintered Mind in August and September will know I have this weird fascination with the question of what we see with our eyes closed. Admittedly, maybe the issue is not quite as important as the nature and pursuit of happiness, which I wrote about Friday.

Setting aside issues about afterimages, "light chaos", visual imagery, etc., here's one possibility: we see the insides of our eyelids. What do you think?

If I close one eye and hold one hand about a foot before the other eye, it's clear that I see my hand, right? Now I bring it slowly closer to the open eye until it eventually covers it completely, blocking out all light (though my eye remains open). Is there a point at which I go from seeing the hand to not seeing the hand? Or, as I sit here hand over eye am I see seeing the hand, though no light whatsoever is reflecting off it or coming into my eye?

It seems to me slightly more natural to say that I see "nothing" than to say that I still see my hand. Maybe, then, we can say that when the hand stops reflecting light into my eye I stop seeing it? But reflecting light into the eye is a strange criterion for seeing, since it implies that I could never see anything that was absolutely black. And we don't want to say that: A good enough coat of black paint doesn't make things invisible -- just very black!

Maybe we can say that I see things as long as they would reflect light shining on them, into my eye, if they were not completely light-absorbent? No, that doesn't work either: Translucent things are visible, so reflecting light into my eye can't be a condition of seeing. And, indeed, my hand is partly translucent, as can be seen if I shine a flashlight through it, while sitting in the dark.

So say I do sit in the dark with a hand completely over an open eye and shine a light through that hand into the eye. Now am I seeing the hand? -- the redness of its blood, say? Or am I just seeing the light? Or both? And if I do see the hand in this case, do I also see it in the case when there is no detectable light coming through? Maybe we should say this, at least: I can see that something (mostly) opaque is covering my eye, even if I can't see the object itself?

All the same questions arise, of course, in the more normal case where one's eyelids are doing the occluding rather than one's hand.

What a magnificent tangle!

The Pursuit (or Not) of Happiness

The Founding Fathers of this country famously ranked "pursuit of happiness" right up there with life and liberty, among our unalienable rights. Psychological hedonism, historically a very important doctrine in philosophy, holds that we in fact pursue nothing but our own happiness. We (or at least Americans) tend to say that "happiness" is among the most important goals in life. But I wonder whether we pursue it very much at all.

Let's assume that happiness is some kind of durable positive mood or emotion or disposition toward positive moods and emotions. (Happiness has of course been defined numerous ways. It's too good a word not to be fought over for its positive resonances.) Something in that ballpark, anyway, seems to be what many Americans have in mind by "happiness".

Now consider this: How does sleep affect your moods and emotions? Surely, it has some important effects. Have you studied them? I seem to have the impression from some of my reading (though I won't look it up now) that mild, short-term, sleep deprivation has a slight mood-elevating effect while longer-term sleep deprivation worsens mood. But I don't really know; and neither you do. (Confess!) But if one of your most important goals in life is your own happiness, shouldn't you try to gain some understanding of this? Most Americans, I think, are mildly sleep-deprived. Is it better for your happiness to stay up that extra half-hour watching TV or reading the newspaper or whatever, or to go to bed more directly?

You say you want happiness over all things, yet you let yourself be sleep-deprived and crabby all day?

Given a choice between going to a restaurant with my family and weeding or doing the dishes, I'd choose going to the restaurant every time. I'm even willing to pay for it -- and if I had more money I'd pay someone else to weed and clean. But I wonder, if I stepped back, whether I'd find myself happier in the restaurant or out in the yard.

I've played a few computer games in my day. Now I can watch my son doing it. What do I see? Often this: Frustration, frustration, frustration, relief. Is the pleasure of relief enough to compensate hedonically for the hours of frustration? Wouldn't I, and wouldn't my son, have been happier enjoying the sunset?

Why aren't we all happiness experts, and remarkable for our hedonic self-care?

Can you say, then, that we really are pursuing happiness, but only doing so with remarkable stupidity? No, no -- better and more natural to say that despite the lip service happiness is not very high among most people's favored pursuits.

(I'm trying to convince Dan Haybron to guest blog here next term. Go check out his website, in the meantime, if you want to learn more about happiness. And shouldn't you want to?)

Attensity

In his 1913 essay "Psychology as the Behaviorist Views It", which is widely credited with (or blamed for!) launching the behaviorist revolt against early introspective psychology, John B. Watson complains

Take the case of sensation. A sensation is defined [by introspective psychologists] in terms of its attributes. One psychologist will state with readiness that the attributes of a visual sensation are quality, extension, duration, and intensity. Another will add clearness. Still another that of order. I doubt if any one psychologist can draw up a set of statements describing what he means by sensation which will be agreed to by three other psychologists of different training.... I firmly believe that two hundred years from now, unless the introspective method is discarded, psychology will still be divided on the question as to whether auditory sensations have the quality of 'extension,' whether intensity is an attribute which can be applied to color, whether there is a difference in 'texture' between image and sensation and upon many hundreds of others of like character (p. 164).

Of course, consciousness studies and introspective psychology are back; and anyone who has delved into the details of scientific or quasi-scientific introspective reports will see the considerable merit in Watson's complaint. And yet it does not follow that there are no facts of the matter to be explored here; maybe it's just hard.

Take the attribute of "clearness". Watson surely has E.B. Titchener in mind here. Titchener characterizes clearness thus:

Clearness... is the attribute which distinguishes the 'focal' from the 'marginal' sensation; it is the attribute whose variation reflects the 'distribution of attention' (1908, p. 26).

Since the term "clearness" has a number of resonances and senses in ordinary language that muddy the issue, Titchener and his students later came to substitute a neologism for it: "attensity". Now, here is the question we must assess to determine if attensity is an attribute of visual sensation: Can two visual experiences be alike in intensity of color, in shape, in resolution of detail, etc., yet differ experientially only in respect of how closely one is attending to them or to their objects -- i.e., in their "attensity"? There are two ways to say no: One might say that degree of attention does not affect visual experience at all, but only later processing, so that my visual experience of this hat before me is exactly the same when I'm attending to it and when I'm not attending to it (assuming all else, such as lighting, angle of eyes, etc., is held constant). Or one might say that degree of attention does affect visual experience but only by means of changing something else, such as the vividness of color or resolution of detail (which of course is another, non-Titchenerian, meaning of "clearness").

Now is this the kind of question we can ever expect an introspective science to answer authoritatively? Or should we join Watson and declare it hopeless? I confess that I myself am torn. I see no reason in principle that we couldn't resolve such matters. Yet the historical divisions of opinion and the muddiness of the answers I expect I would get if I polled people on the matter, and the feeling of lack of progress and the irresolvability of debates between entrenched opponents -- all that gives cause for pessimism....

Brief Hiatus

Regular visitors will know I usually post on a MWF schedule. I'll be out of town for a long weekend, Friday through Monday, and I won't be able to post again until next Wednesday. (I'll be away for my annual "Geekend": Some old friends and I rent a cabin in the mountains near Palm Springs and do old-fashioned pencil-and-paper roleplaying games morning to midnight for three days straight, fueled mainly by coffee and Doritos. Yes, yes, I know. That's why we call it Geekend.)

A Plea for Stories about Virtue and Wickedness in Ethicists

I beg a favor. Tell me stories about the ethics professors you've known -- stories of their virtue or malfeasance, the more detail the better. Post them as comments on this post, or email me at eschwitz at domain: ucr.edu.

I ask you this not out of pure gossip-love, but to good philosophical ends -- in connection, that is, with my reflections on the relationship between moral reflection and moral behavior.

I'm interested in anecdotes here, not generalizations (to get generalizations, I will be conducting a survey in December), with enough detail to give a real flavor of the incident.

(If you write a long comment, I recommend that you do so first in your word processing program, then paste it into the comments section. Occasionally Blogger crashes posting a comment, and it can be frustrating when that comment is long!)

Philosophers' Carnival #37...

... is at Hell's Handmaiden. (Thanks to the Handmaiden!)

The next carnival, Nov. 6, will be right here at The Splintered Mind. I see that no one has signed up yet to host the Nov. 27 carnival. So if you have a blog of your own, think about volunteering!

Metaphysics, What?

Philosophers, I suppose, sometimes do metaphysics. No, let me put it more cautiously. Philosophers engage in certain practices, which they sometimes call "metaphysics". I can tell fairly well what sorts of practices will be labeled in this way -- e.g., much of David Lewis's work and the ensuing discussions, analytic philosophy of mind as driven by thought experiments, discussions of "personal identity". But is this really metaphysics? What the heck is metaphysics, anyway?

Here's one view. Let's call it the "mystical view" -- because really it is rather mystical, though many hard-nosed, atheistic philosophers seem implicitly (or even explicitly) to accept it. Metaphysics is the discovery, by a priori armchair reflection without depending upon anything empirical, of necessary truths of the universe -- truths such as that causes must precede effects, and that a functional duplicate of me must necessarily have (or will not necessarily have) conscious experience. Such facts are supposed hold true regardless of our concepts, to be independent of our (contingent) ways of thinking about things. We tap into them not by looking at the world but rather by... well, that's the mystical part. How, exactly, do we learn about the outside universe (not just our own minds) without looking at it? Those philosophers who have gamely tried to explain the process in question -- George Bealer and Laurence BonJour, for example -- have tied themselves in such knots, been forced to wave their hands at such absolutely crucial junctures, and if I may be frank have failed so utterly as to make the hopelessness of their project even more evident after having read them than one might have thought beforehand.

Here's another view of what's going on. Call this the "no metaphysics" view. What philosophers learn from their armchairs, without looking at the world, are facts not about remote possible worlds accessible in no other way, or facts about the deep metaphysical structure of the universe, but rather facts about their own minds -- facts, especially, about their concepts. What else would one learn about, sitting in one's armchair? We learn that our concept of "cause" is a concept involving the temporal priority of the cause to the effect, our concept of a person is thus-and-such, etc.

But of course learning about our concepts is learning not metaphysical truths in the sense that philosophers ordinarily mean the phrase but rather learning contingent empirical facts about how we think. The concepts so delivered may be revisable in the face of empirical evidence (see Friday's post). And furthermore, they are empirically, psychologically explorable: There's more than one way to learn about "our" concepts. Philosophers in the armchair might not be getting the story right, or they may be an unrepresentative sample.

The philosophical practices labelled "metaphysics", then, have two uses, as I see it, neither of which is the discovering of metaphysical truths: (1.) They provide a kind of evidence about how people (a certain type of people, with certain habits of reflection and standards of inquiry) happen to conceptualize things; and (2.) (more interestingly, to me) they provide recommendations about how we should conceptualize things. If construed in this way, such recommendations should be evaluated pragmatically, in terms of their usefulness in organizing our way of thinking about matters of concern to us.

Getting clear about the pragmatic standard of evaluation can, I think, help us sort through and evaluate competing "metaphysical" claims about personal identity, causation, and the like. So, for example, in my work on belief, which could easily be misconstrued as metaphysics, I advocate a broad dispositional approach as giving us the best tool for talking about and characterizing the kinds of case that interest me most in believing -- what I call the "in-between" cases of gradual learning and forgetting, self-deception, confusion, ambivalence, irrationality, and failure to think things through.

Intuitions in the Sandbox

A graduate student recently reminded me of an essay I'd written in 1998 with Alison Gopnik, a developmental psychologist at U.C. Berkeley. He appears to be just about the only person who liked it. But maybe I'm wrong about that -- maybe he was merely being polite!

The essay begins with a dialogue pertinent to the relationship between empirical psychology and philosophical intuition, which is an increasingly hot topic these days. The dialogue is, I think, amusing, provocative, and self-standing (it was entirely written by Alison), and for some reason I feel like inflicting it on readers of this blog.

To understand the dialogue it's necessary to know that developmental psychologists now think that children progress from, at age 3, not realizing that beliefs can be false to knowing, by age 4, that beliefs can be false. (Surprising as this conclusion may be, it is now orthodoxy in developmental psychology and is supported by hundreds of studies.)

Here's the dialogue, conceived of as between two three-year-olds in a sandbox, Phil and Psyche.

Psyche: You know, Phil, something’s been bothering me. You know how beliefs are always true? Well, an odd thing happened the other day. My big brother saw my mom put a piece of chocolate in the cupboard and then left to play Nintendo, and while he was away my mom took the chocolate out of the cupboard and put it in the drawer. When my brother came back, he went straight to the cupboard and said loudly, several times, that he was sure the chocolate was in there. But of course, it was really in the drawer. So I have this idea: Could it be that he had a belief that was just like ordinary beliefs, except false?

Phil: My dear Psyche, as I have so often pointed out to you before, your confusion is due to a category mistake. You are treating the truth of beliefs as if it were an empirical matter. Actually, it is simply a conceptual fact about beliefs that they are always true. Indeed, we might say that it is criterial for a belief to be a belief that it be true. Look, consult your intuitions, consult the intuitions of anyone else in the sandbox. All of us agree, immediately, intuitively, without inference or theory, that all beliefs are true. Ask yourself what a belief is. What else could it be but a true representation of events?

Psyche: But couldn’t we all be wrong? Couldn’t there be an alternative way of conceiving of belief that none of us happen to subscribe to now?

Phil: Another category mistake. When I say that beliefs are necessarily true, this isn’t a mere contingent psychological fact about the concepts of all us three-year-olds. It’s an eternal, platonic, philosophical fact about the nature of belief and truth.

Psyche: Well, what about my brother?

Phil: He is probably participating in an alternative form of life. I always thought he was kind of weird.

Psyche: But you see, it isn’t just him. It even seems to be me. Since the chocolate incident, wherever I look, I see evidence that beliefs may be false. Why just yesterday, a woman came into the daycare center with a candy box and I said “Candy!” and then she opened the box and there were pencils inside. I know intuitively that I must have thought there were pencils in the box all along, and of course that’s what I told her when she asked me. But then why did I say “Candy!”? Am I turning into a madwoman?

Phil: (gravely) I fear you may have a worse affliction. I fear you are turning into a cognitive psychologist. As I was saying just the other day, “It would be dangerous to deny from a philosophical armchair that cognitive psychology is an intellectually respectable discipline, provided, of course, it stays within proper bounds.” [Apparently a copy of John McDowell's 1994 book, Mind and World found its way onto the picturebook shelf.] This is what happens when those bounds are breached.

Psyche: But surely there must be some explanation?

Phil: Philosophy does not provide explanations, only diagnoses. (Intones) Of that we cannot speak, thereof we must be silent....

The remainder of the essay was conceived of simply as the exposition of the main idea of this dialogue: that philosophers who think that their intuitions reveal necessary metaphysical truths about the world are as confused as Phil. Our intuitions derive from empirical sources (or else, no better, were written into us innately by natural selection), and we should hold them up to revision as new empirical evidence comes in. I don't think Quine or Carnap would have disagreed....

You can find the entire essay here.

The Nisbett-Wilson Myth

It seems like every time I present my work on our poor knowledge of our own conscious experience (e.g., here, here, and here) before a large group, someone says, "But didn't Nisbett and Wilson show that back in the '70s?"

Richard Nisbett's and Timothy Wilson's 1977 essay, "Telling More Than We Can Know" is one of the most-cited papers in the history of psychology. Looking at cases in which, for example, people seem to show amazing ignorance of the bases of their preference for a particular pair of socks, Nisbett and Wilson conclude that "people may have little ability to report accurately on their cognitive processes" (p. 246). In the psychological and philosophical lore, this conclusion has been amplified into a general repudiation of our knowledge of our own minds.

Yet Nisbett and Wilson themselves are quite clear that they do not intend their thesis that way. In a section titled "Confusion Between Content and Process" they draw a sharp distinction between "cognitive processes" (roughly, the causal process underlying and driving our judgments, decisions, emotions, and sensations) and mental "content" including those judgments, decisions, emotions, and sensations themselves. They explicitly limit their skepticism to the former. Regarding the latter they say that such "private facts... can be known with near certainty" (p. 255). In other words, despite the mythology, Nisbett and Wilson are not skeptics about introspective report of conscious experiences. They are skeptics about introspective knowledge of the causes of those experiences. They are skeptical about our knowledge of why we selected a particular brand of socks, not about the fact that we do judge them to be superior or about our sensory experience as we select them.

Wilson continues to be explicit about this. In his recent (2002) book Strangers to Ourselves, he argues that we have poor knowledge of "the adaptive unconscious". He distinguishes this from consciousness and restricts his skepticism to the former (e.g., p. 17-18).

So enough sloppy, second-hand references to Nisbett and Wilson! If you want to cite psychologists who truly argue for the view that we often go wrong in describing our stream of conscious experience, look neither to them, nor indeed to the behaviorists (who were often suspicious of the very idea that the phrase "stream of conscious experience" referred to anything worth exploring at all), but rather to early 20th-century introspective psychologists like E.B. Titchener and G.E. Mueller!

Ephemeral Belief?

I've often defended the view that we should think of beliefs (as opposed to temporary judgments) as involving a broad array of stable dispositions -- dispositions to act, react, think, and feel in ways appropriate to the belief, across a spectrum of situations. But here's an example that troubles me.

I'm at a party. Someone introduces himself -- "Jerry". I shake his hand and say "Hi, Jerry!" Five seconds later I cannot tell you his name. (Admit it, this happens to you too!)

Now in this case, it seems both that I believe (however temporarily) that his name is Jerry and that I don't form a broad array of stable dispositions pertinent to that belief. If so, of course, believing can't be a matter of having a broad array of stable dispositions -- contra me!

I see two responses. The first is to reject the intuition that I believe his name is Jerry (for those five seconds). (This is what Krista Lawlor said when I pressed her on the issue during her visit last week.) Maybe it's a weird, marginal case of the sort our intuitions really weren't meant to handle. We can, of course, (as philosophers) define the technical term "belief" however we want; we needn't hew to intuition in every case; and there's something valuable in reserving the term "belief" only for states in which one has a broad array of stable dispositions.

The second response is to reject stability: Maybe only breadth is necessary. For five seconds, my dispositions are all right, perhaps, across the board -- I would say "Jerry" to myself when thinking of him, I'd assume someone who said that name was talking about him, I'd greet him with that name, I'd feel surprised if someone called him "Larry", etc. -- and that's enough for belief. The broad array of dispositions changes quickly enough; it just won't stay put.

I'm not entirely happy with either answer.

Unqualified Judgment Without Belief?

Krista Lawlor gave a very interesting talk here at UC Riverside Wednesday, which has me thinking again about belief. (Admittedly, getting me thinking about belief isn't a very hard thing to do!)

It seemed implicit in her paper, and it came out more explicitly in discussion afterward, that Lawlor regards believing as a matter of having a broad, stable array of dispositions -- i.e., having general patterns of thought, reaction, planning, implicit assumption, etc., in conformity with the content of the belief -- as opposed to belief being merely a matter of having some thought or judgment or opinion occurring to one in a moment; and indeed the two phenomena often come apart. (For my endorsement of this view, see this post and this essay and this essay too.)

To use one of Lawlor's examples, someone raised in a family committed to the reality of homeopathy might as a result of taking a chemistry class become convinced that homeopathy doesn't work, in the sense of reaching a sincere judgment like this: "Something so diluted that not even a single molecule of the supposedly curative substance remains must be inert!" And yet that person might not yet be ready to throw his homeopathic remedies in the trash, might feel uncomfortable not taking those remedies in certain cases, might in unguarded moments find himself thinking "so-and-so needs such-and-such a remedy", etc. There's a certain amount of cognitive inertia between what we sincerely judge in the moment and what we enduringly, dispositionally believe.

Or here's an example from my essay linked to above: Someone might sincerely and unhesitantly and unqualifiedly endorse the proposition that all the races are intellectually equal, yet be so biased in her implicit reactions and background assumptions about people that we wouldn't want to say that she really should be described as fully, dispositionally believing that.

No one is more on board with Lawlor on such matters than I, yet my colleagues were not all entirely convinced!

Here's the most common objection I heard, in the comments and in discussion with Lawlor before and afterward: If your dispositions don't fall entirely into line with your judgment, then either your judgment must not be wholly unqualified, or you must be the victim of some sort of weird irrationality.

Now I'm not sure exactly what we ought to call "rational", but in some cases at least I think it makes considerable sense to have a sort of dispositional inertia. We don't want to cast aside long-held beliefs that ramify through our lives with the advent of a single unqualified judgment. Suppose the homeopathy case were, instead, a case of someone being converted to libertarianism by Ayn Rand. Fortunately, such conversions often fade quickly, fail to ramify, are conversions only of temporary judgment, not in the broad array of one's dispositions. (Apologies to libertarians!) So I hesitate to think of the divergence between unqualified judgment and broad, dispositional belief as simply irrational.

No?

Do Ethicists Steal More Books?

When I was young, my father and I used to joke about stealing Bibles, or breaking into a Christian store and making off with a load of crucifixes. The irony appealed to us, on the assumption that an important part of wanting a Bible or a crucifix is endorsing a set of values that includes the repudiation of theft. There's something likewise ironic, it seems, in stealing an ethics text (or should I say deliciously wicked?).

One might expect Bibles and books extolling the life of virtue to be relatively less stolen than similarly popular books with no moral message. On the other hand, given my sense that ethicists, on the whole, behave no better than the rest of us, maybe we shouldn't expect a difference. In casual conversation, I've sometimes heard it remarked that ethics books seem, indeed, more likely to be missing from libraries than books in other areas of philosophy -- which would comport nicely with the sense some people have of the particular viciousness of ethics professors. However, the impression that ethics books are more likely to be stolen might derive from their simply being more popular, or it might be a saliency effect -- perhaps we're more likely to be struck by and remember a theft of Kant's Groundwork of the Metaphysics of Morals than a theft of Kripke's Naming and Necessity.

Here at the University of California, we have access to a system called Melvyl, which gives circulation information on all the books in the University of California system. The main campus libraries at Berkeley, Irvine, Los Angeles, Riverside, San Diego, and Santa Cruz also give due date information, including for overdue books. So we can inquire: Are ethics books more or less likely to be overdue or missing from these UC campuses than other philosophy books?

I looked at the book reviews in Philosophical Review from 1994-2001. I included in my survey books that were clearly in ethics (excluding philosophy of action, political philosophy on proper governance [rather than private virtue], and other borderline cases). As a comparison class, I also looked at books that were clearly outside of ethics if the review started on a page number divisible by four. This gave me 76 ethics books and 67 non-ethics books. Almost all these texts were held by at least 5 of the 6 campuses; some texts had multiple copies at a single campus.

The ethics books were listed as off the shelf (checked out or missing) in 73 cases (between the 6 campuses) out of 452 held copies, for an off-shelf rate of 16.1%. Of these, 8 were overdue or missing (5 missing or lost; 1 more than 1 year overdue; 2 less than one year overdue), for a 1.8% deliquency rate per copy. 11.0% of the off-shelf books were delinquent.

The non-ethics books were listed as off the shelf in 66 cases out of 379 held copies, for an off-shelf rate of 17.4%. Of these, 7 were overdue or missing (actually, all 7 were simply missing, none overdue), for a 1.8% delinquency rate per copy. 10.6% of the off-shelf books were delinquent.

These numbers are too small to draw any definite conclusions, but they do seem to suggest that, among philosophical books prominent enough to be reviewed in Philosophical Review, ethics books are checked out and stolen at very nearly the same rate as non-ethics books -- neither more nor less.

The University of California has a pretty good system for tracking down overdue books. I wonder to what extent the low delinquency rates are due to good enforcement rather than the conscientiousness of the patrons. In this connection, it would be interesting to do a study of libraries that depend primarily on the honor of the patrons. The UCR Philosophy Department Library is an example of the latter (as opposed to the main library, Rivera, whose holdings are included in Melvyl, described above); but unfortunately there's no systematic record of its holdings.

If any readers of this blog have access to the circulation records of a consortium of libraries, or have access to information from which they could infer deliquency rates in libraries that depend mostly on the honor of the patrons, and are interested in exploring this issue farther, I'd love to hear from you!

Paranormal Phenomena and Substance Dualism

If you're going to be a dualist -- that is, if you differentiate the mental from the physical -- I think you ought to be a good old-fashioned substance dualist. You ought, in other words, to embrace the idea that there are distinct mental and material substances. The more fashionable form of dualism in analytic philosophy these days, "property dualism", which distinguishes mental from physical properties, as conceptually distinct, while denying that there is any distinctly mental substance, seems to me too far removed from the questions that we should care about in the dualism-materialism debate -- questions such as whether we have immaterial souls that could persist into an afterlife (property dualism, like materialism, says no), and whether our thoughts depend solely upon physical goings-on (property dualism, like materialism, says yes, for all practical purposes). I've not yet been convinced that I should care much about what would be the case in "logically possible worlds" where the laws of physics and psychology are suspended -- the sort of thing property dualists such as Chalmers want us to think about. (But if you are going to think about such things, Chalmers is a model of clarity and intelligence.)

The truth of substance dualism is empirically explorable, as the debate between materialism and property dualism (with its focus on the merely logically or "metaphysically" or "conceptually" possible) appears not to be. Of central relevance to the question, of course, is the dependency of our mental processes on how things stand in the material world -- on our brains in particular. The more it seems that mental life depends on and covaries with brain activity, the worse for substance dualism. With the advance of neuroscience, substance dualism isn't looking so good, I'd say.

However, there is one class of evidence that philosophers rarely explore and which, if it were to pan out, would spell serious trouble for materialism; that is "paranormal" or "psi" phenomena -- especially direct mind-to-mind communication (without a physical medium) and out-of-body experiences.

The evidence for paranormal phenemona is mixed. It is not as decisively negative as most contemporary academics tend to assume. The work of Daryl Bem (on direct mind-to-mind communication) and Pim Van Lommel (on out-of-body experiences in near-death situations) especially comes to mind.

Bem's classic "Ganzfeld" experiments (e.g. Bem & Honorton 1994 in Psych Bulletin) require a "sender" and a "receiver" to be sequestered in separate compartments; the "sender" is given a randomly selected image to concentrate on and to try to send; the "receiver" is to describe her thoughts and images aloud for 30 minutes. Finally the receiver is presented with four pictures (one the target) and asked to rate the similarity of each to her mentation during the 30 minute period. Results are generally above chance.

Bem, an eminent Cornell psychologist, knows how to design a study. Reading through his work, I generally think to myself, "If this were about anything else, I'd say this was a perfectly designed and utterly convincing study. He has controlled for everything." Carl Sagan was surely right in saying extraordinary claims require extraordinary evidence; but how extraordinary, exactly, is sufficient? Do we need to consider, for example, that Bem might simply be lying, or have been systematically deceived by unscrupulous collaborators and subjects?

Pim Van Lommel, similarly, has published work in the Lancet and elsewhere, work done in accord with typical scientific standards and suggestive of the reality and frequency of near-death experiences. Van Lommel has evidence that patients during cardiac arrest, with eyes closed and severely compromised brain function, were in some cases able to acquire otherwise unavailable information about happenings in the outside world (e.g., detailed descriptions of the what the doctor did with the patient's dentures) reported by the patient as having been seen from above. Van Lommel (personal communication) has even tried prospective studies of this latter sort of phenomenon, posting notes high in rooms where patients near cardiac death are being treated, notes facing the ceiling; but unfortunately, he reports, patients reporting near-death out-of-body experiences seem to be much more focused on their bodies and their religious experiences than on the contents of such notes!

I'm not saying we should accept Bem and Van Lommel; but I do think we should take them seriously. This is where I'd like to see the action in debates about dualism, rather than on questions such as the conceivability (or not) of various possibilities (e.g., "zombies"), if one suspends the laws of physics!