Friday, November 08, 2013

Expert Disagreement as a Reason for Doubt about the Metaphysics of Mind (Or: David Chalmers Exists, Therefore You Don't Know)

Probably you have some opinions about the relative merit of different metaphysical positions about the mind, such as materialism vs. dualism vs. idealism vs. alternatives that reject all three options or seek to compromise among them. Of course, no matter what your position is, there are philosophers who will disagree with you -- philosophers whom you might normally regard as your intellectual peers or even your intellectual superiors in such matters – people, that is, who would seem to be at least as well-informed and intellectually capable as you are. What should you make of that fact?

Normally, when experts disagree about some proposition, doubt about that proposition is the most reasonable response. Not always, though! Plausibly, one might disregard a group of experts if those experts are: (1.) a tiny minority; (2.) plainly much more biased than the remaining experts; (3.) much less well-informed or intelligent than the remaining experts; or (4.) committed to a view that is so obviously undeserving of credence that we can justifiably disregard anyone who espouses it. None of these four conditions seems to apply to dissent within the metaphysics of mind. (Maybe we could exclude a few minority positions for such reasons, but that will hardly resolve the issue.)

Thomas Kelly (2005) has argued that you may disregard peer dissent when you have “thoroughly scrutinized the available evidence and arguments” on which your disagreeing peer’s judgment is based. But we cannot disregard peer disagreement in philosophy of mind on the grounds that this condition is met. The condition is not met! No philosopher has thoroughly scrutinized the evidence and arguments on which all of her disagreeing peers’ views are based. The field is too large. Some philosophers are more expert on the literature on a priori metaphysics, others on arguments in the history of philosophy, others on empirical issues; and these broad literatures further divide into subliteratures and sub-subliteratures with which philosophers are differently acquainted. You might be quite well informed overall. You’ve read Jackson’s (1986) Mary argument, for example, and some of the responses to it. You have an opinion. Maybe you have a favorite objection. But unless you are a serious Mary-ologist, you won’t have read all of the objections to that argument, nor all the arguments offered against taking your favorite objection seriously. You will have epistemic peers and probably epistemic superiors whose views are based on arguments which you have not even briefly examined, much less thoroughly scrutinized.

Furthermore, epistemic peers, though overall similar in intellectual capacity, tend to differ in the exact profile of virtues they possess. Consequently, even assessing exactly the same evidence and arguments, convergence or divergence with one’s peers should still be epistemically relevant if the evidence and arguments are complicated enough that their thorough scrutiny challenges the upper range of human capacity across several intellectual virtues – a condition that the metaphysics of mind appears to meet. Some philosophers are more careful readers of opponents’ views, some more facile with complicated formal arguments, some more imaginative in constructing hypothetical scenarios, etc., and world-class intellectual virtue in any one of these respects can substantially improve the quality of one’s assessments of arguments in the metaphysics of mind. Every philosopher’s preferred metaphysical position is rejected by a substantial proportion of philosophers who are overall approximately as well informed and intellectually virtuous as she is, and who are also in some respects better informed and more intellectually virtuous than she is. Under these conditions, Kelly’s reasons for disregarding peer dissent do not apply, and a high degree of confidence in one’s position is epistemically unwarranted.

Adam Elga (2007) has argued that you can discount peer disagreement if you reasonably regard the fact that the seeming-peer disagrees with you as evidence that, at least on that one narrow topic, that person is not in fact a full epistemic equal. Thus, a materialist might see anti-materialist philosophers of mind, simply by the virtue of their anti-materialism, as evincing less than a perfect level-headedness about the facts. This is not, I think, entirely unreasonable. But it's also fully consistent with still giving the fact of disagreement some weight as a source of doubt. And since your best philosophical opponents will exceed you in some of their intellectual virtues and know some facts and arguments, which they consider relevant or even decisive, which you have not fully considered, you ought to give the fact of dissent quite substantial weight as a source of doubt.

Imagine an array of experts betting on a horse race: Some have seen some pieces of the horses’ behavior in the hours before the race, some have seen other pieces; some know some things about the horses’ performance in previous races, some know other things; some have a better eye for a horse’s mood, some have a better sense of the jockeys. You see Horse A as the most likely winner. If you learn that other experts with different, partly overlapping evidence and skill sets also favor Horse A, that should strengthen your confidence; if you learn that a substantial portion of those other experts favor B or C instead, that should lessen your confidence. This is so even if you don’t see all the experts quite as peers, and even if you treat an expert’s preference for B or C as grounds to wonder about her good judgment.

Try this thought experiment. You are shut in a seminar room, required to defend your favorite metaphysics of mind for six hours (or six days, if you prefer) against the objections of Ned Block, David Chalmers, Daniel Dennett, and Saul Kripke. Just in case we aren’t now living in the golden age of metaphysics of mind, let’s add Kant, Leibniz, Hume, Zhu Xi, and Aristotle too. (First we’ll catch them up on recent developments.) If you don’t imagine yourself emerging triumphant, then you might want to acknowledge that the grounds for your favorite position might not really be very compelling.

It is entirely possible to combine appropriate intellectual modesty with enthusiasm for a preferred view. Consider everyone’s favorite philosophy student: She vigorously champions her opinions, while at the same time being intellectually open and acknowledging the doubt that appropriately flows from her awareness that others think otherwise, despite those others being in some ways better informed and more capable than she is. Even the best professional philosophers still are such students, or should aspire to be, only in a larger classroom. So pick a favorite view! Distribute one’s credences differentially among the options. Suspect the most awesome philosophers of poor metaphysical judgment. But also: Acknowledge that you don't really know.

[For more on disagreement in philosophy see here and here. This post is adapted from my paper in draft The Crazyist Metaphysics of Mind.]


John Baez said...

It's interesting to list some subjects other than philosophy where such radical disagreement exists... and some where it doesn't. But I'm not sure you'll like the results.

Eric Schwitzgebel said...

John, what do you have in mind? Some of the potential problem cases (e.g. global warming, evolutionary theory) can be escaped by triggering clauses 1-4, if we can agree that only a tiny minority of the best informed experts denies. (Admittedly, there might be some risk of circularity in determining who is an "expert".)

David Duffy said...

In the case of scientific disagreement, I would think most participants have an expectation that further evidence will eventually clarify which if any position is correct. A certain amount of the metaphysics of mind will be like this, as opposed to competing stances in, say, ethics.

The Uncredible Hallq said...

I want to like this post, because the specific issue it focuses on - philosophy of mind - is one where I feel a lot of confusion myself.

But I can think of examples from within philosophy where I'm pretty confident of my opinion even though I'm not sure criteria 1-4 apply as reasons to discount the opinions of people who disagree. Namely:

1) Rejection of skepticism and idealism. Those are "tiny minority" positions as much as anything in philosophy is, but are they tiny enough, by your standards?
2) Atheism. Theism is definitely in the minority, but also definitely not a "tiny" one. You could argue (2) and/or (4) apply, but that's going a little far even for my tastes (and I don't have much regard for theistic philosophers).
3) Compatibilism. This is maybe the one where I'm most vulnerable, but I find Eddy Nahmias' x-phi work on the topic pretty damn convincing and somehow I'm not moved by knowing there are a fair number of libertarians and hard determinists out there.

Eric Schwitzgebel said...

Thanks for the comments, David and Uncredible! (It seems like a while since I've heard from either of you!)

David: I agree about the scientific case. My inclination is to think that empirical evidence is relevant both to ethics and to metaphysics of mind, but that the medium-term prospects are poor for finding *decisive* evidence favoring one broad type of view over all competitors. So I'm not sure about the disanalogy. Cross-cultural discovery and life experience and empirical science can have a big impact on ethical views, e.g., about sexual morality; and I'm not sure this is less so than evidence from cosmology, microphysics, and psi research on whether there is something that transcends the material.

Eric Schwitzgebel said...

Uncredible: I propose this rule of thumb: If a minority position is held by X% of the experts, then the argument from disagreement cannot compel you to ascribe more than X% credence to it. So if 5% of philosophy experts are idealists, the argument from disagreement cannot compel you to ascribe more than 5% credence to it. And less credence might be acceptable, too, since I don't think we need to accept the "equal weight" approach.

On points 2 and 3, I'm inclined to accept that the extent of expert disagreement *should* lead one to reserve a non-trivial portion of one's credence space for theism and libertarianism -- though maybe again substantially less than the X% of experts who are theists and libertarians. Some reasons to go under X% might be simply self-confidence and trust in one's judgment, *plus* some suitably weakened versions of 2-4. I'm inclined to think that > 95% credence in atheism or compatibilism, though, starts to push on the borders of irrational philosophical self-confidence, once one considers one's position on the philosophical world stage, including perhaps the possible future evolution of philosophy which might make some of our views look pretty off the mark in a couple of centuries!

PS on my agnosticism: I think highly unorthodox theologies are worth considering, e.g., views on which we are beings instantiated in computer programs run by children for entertainment (see the "Crazy Cosmology" section of "The Crazyist Metaphysics of Mind), in which case the children and/or the computer programmers might rightly be seen as divinities relative to us. (I also have a couple sci-fi stories about this.)

Marco Devillers said...

Democratic philosophy? This reminds me of an Economists poster: "A billion flies can't be wrong, eat shit!"

This was, of course, a comment on the market never being wrong.

Sorry, no offense meant, but I really don't think it should work the way you propose.

Eric Schwitzgebel said...

Marco: I'd be interested to hear your argument why not.

Angra Mainyu said...

Uncredible and Eric,

On the issue of atheism-theism, there seem to be two further complications (at least):

a. While most philosophers are non-theists, the vast majority of philosophers of religion are theists. This raises a question of relevant experts when it comes to assess the matter.

b. It seems to me (I guess I might be mistaken about that, but I'd say at least it's the case for philosophers of religion) that most theist philosophers are Christians, and that would make Christianity a minority among philosophers but not a tiny one – and, also, Christianity seems to be in the majority among philosophers of religion.
Granted, there are different forms or versions of Christianity, but for example, the belief that Jesus resurrected (physically or otherwise) is held by at least nearly all of those philosophers, so it's also not a tiny minority, it seems to me.
Yet, a > 95% credence in the view that, say, Jesus did not resurrect, (physically or otherwise) is fine. In fact, I would say that a 5% or even a 1% credence in the view that he did resurrect is not okay, after considering the matter to at least some degree of depth, and regardless of the question of theism/atheism.
I would say that is definitely the result of bias, but that also provides good grounds for the view that theists are generally biased, since their theism is plausibly (and at least in most cases) not tied to the sophisticated theistic arguments that are discussed in present-day philosophy of religion, but to their Christian belief.

On a related note, I would suggest replacing (2) by (2'), which would be:

(2'): Plainly heavily biased.

The reason is that, it seems to me that whether it's proper to hold that the fact that group of experts G1 hold that P1 is true provides only negligible evidence in support of P1 due to bias of the experts in G1 does not depend on how biased some other group of experts are. For example, if plenty of Muslims were to enter philosophy of religion and they denied Jesus' resurrection (claiming, say, that he went to heaven without dying instead), that would not have any impact on an assessment of how little evidence for the resurrection of Jesus is provided by the fact that Christian philosophers of religion hold it happened.

Marco Devillers said...

Eric: I can't say I thought it that much through. It seems unlikely people can work with weighted belief systems.

I am not sure how I can give you an answer. You hint at modes of working of the human brain, and what underlying logic could be able to be ascribed to that. The question whether truth exists.

I am somewhat of an existentialist absurdist. Truth doesn't exist, there are no answers, everything you believe is (provably) wrong. Stuff like that.

Back to the mundane.

Aren't you supposed to believe in the technical quality of an argument deriving from a number of things you perceive as axiomatic? I do. And aren't all things you decide upon superior to other people's lines of reasoning?

You suggestion of a weighted decision is 'inhumane.' Darwin decided the human mind doesn't work like that. One could, of course, frivolously expect to build other intelligences on weighted logics. Maybe there is a fundamental reason one could, or can't, do that. As I said, I didn't think it much through.

Sorry for rambling.

Eric Schwitzgebel said...

Angra: Thanks for the very interesting, thoughful reply! Assessments of expertise and bias are going to be tricky, and those assessments will be influenced by opinions on the issue in question in a way that I think makes matters complicated and should give us pause, though I don't think complete epistemic surrender is the most rational result.

You raise a good point about (2). The problem with (2') as a substitute, as I see it, is that it seems more tractable to evaluate comparative bias than to try to weigh bias on some absolute scale. Also one slightly odd result of (2') would be that if everyone is heavily biased the argument from disagreement is weakened, whereas I'm inclined to think that in an arena of heavy bias (like religion) is where people often think the argument from disagreement has some weight.

Eric Schwitzgebel said...

Marco: I agree that weighted belief systems aren't the way that people tend to think about metaphysical issues; all-or-nothing thinking is easier. But I think we can rise to the occasion!

The Uncredible Hallq said...

Re: Eric on theism. I guess a lot depends on how you define "theism."

If you're talking about orthodox omnimax monotheism, it seems pretty clear to m that the only reason philosophers take that idea more seriously than they take Greco-Roman polytheism is that the former idea is what's dominant in the broader culture, and the reasons for its dominance have nothing to do with the merits of the idea. On top of that, omnimax monotheism has the *additional* burden of the problem of evil, and current theistic responses to the problem of evil are just awful.

(I say this having read Plantinga et al., and no there is not a consensus that Plantinga solved anything, the fact that many theistic philosophers have put a lot of energy into claiming a non-existent consensus is one of the things that's so pitiful about their responses.)

But once you get into things like Bostrom's simulation argument, I admit I'm not entirely sure what to think of that.

Angra Mainyu said...


Thanks for your thoughtful reply as well.
I do agree that epistemic surrender is not the way to go.
With regard to (2) vs. (2'), you make a number of interesting points.
My take on some of the issues involve would be:

a. On the issue of how easy it is to evaluate whether (2) or (2') obtains, personally, I tend to think that (2') is probably generally easier, since one may evaluate whether a person is heavily biased depending on the arguments of that person, other beliefs, etc., and without having to factor in whether other people are biased as well. However, I reckon there may be cases in which the comparison may help.

b. Regarding the results, in practice, I tend to think that in many, perhaps most cases, (2) and (2') will go together.
More precisely, as long as one can tell that at least some experts are not heavily biased, (2) allows one to disregard the assessments (not the arguments but the claims themselves as evidence for some proposition, etc.) of the plainly heavily biased experts (since they're plainly much more biased than the rest, as far as one can tell), which (2') allows as well. On the other hand, neither (2) not (2') allows one to disregard the assessments of experts who aren't plainly heavily biased, it seems to me (since "much more biased than the rest" seem to imply heavily biased, though there is some vagueness here).
A difference would seem to happen in cases in which all experts are plainly heavily biased, or at least some are plainly heavily biased, and it's unclear whether the rest are, in which case (2) does not allow one to disregard the assessments of the heavily biased experts as evidence (i.e., give them negligible weight), whereas (2') does, which I think is the right result.

That said, I'm not sure how that would give an odd result in philosophy of religion, but I might be missing the case you have in mind, so I'd like to ask for a bit more info on the odd result you have in mind (e.g., what's the proposition being assessed? What's the position (if any) of the person assessing the disagreement argument?).

Marco Devillers said...

Hallq: I think that there are lots of reasons why monotheism was preferred over polytheism at some point in history. It has more merits, but I assume that wasn't what you meant.

The Uncredible Hallq said...


I'm confused about what you think I meant. I'm personally a fan of Hume's explanation of omnimax theology:

"It may readily happen, in an idolatrous nation, that though men admit the existence of several limited deities, yet is there some one God whom, in a particular manner, they make the object of their worship and adoration. They may either suppose that, in the distribution of power and territory among the Gods, their nation was subjected to the jurisdiction of that particular deity; or, reducing heavenly objects to the model of things below, they might represent one God as the prince or supreme magistrate of the rest, who, though of the same nature, rules them with an authority like that which an earthly sovereign exercises over his subjects and vassals. Whether this God, therefore, be considered as their peculiar patron, or as the general sovereign of heaven, his votaries will endeavor by every art to insinuate themselves into his favor; and supposing him to be pleased, like themselves, with praise and flattery, there is no eulogy or exaggeration which will be spared in their addresses to him. In proportion as men’s fears or distresses become more urgent, they still invent new strains of adulation; and even he who outdoes his predecessors in swelling up the titles of his divinity, is sure to be outdone by his successors in newer and more pompous epithets of praise. Thus they proceed; till at last they arrive at infinity itself, beyond which there is no farther progress."

Marco Devillers said...

Yeah well. I am not a theologist, neither am I a philosopher. Absurdists make lousy philosophers but great writers.

I believe monotheism has merits over polytheism from a social Darwinistic perspective. A clarified doctrine, a simpler political system, a ground for absolutist arguments why power is distributed in certain manner, a manner of generating more devout people, simplified psychological arguments , a simplified theological base to discuss the origin of religious thought. Just to name a few merits.

I stopped but the list why monotheism has more merits than polytheism is rather endless.

Anonymous said...

Why worship any god other than the most awesome one? I'd rather have Zeus as my patron than the tiny unknown god of dust bunnies.

Also as technology advances various claims become far less amazing.

Nowadays we might send a fighter plane into the sky and while Zeus tries unsuccessfully to not hit lightning rods with his lightning bolts we would blow him up with a missile.


Eric Schwitzgebel said...

Marco/Uncredible/GNZ: It's an interesting set of questions! I have a firm opinion myself but maybe some cross-cultural comparisons would help, including of very large religions like Hinduism and Buddhism.

Angra: That seems right about the cases of agreement and disagreement. Where all groups of experts are heavily biased, though, I think we should regard disagreement as epistemically important. In the religion case, if the atheists are as biased as the various groups of theists (and no better informed etc.) then we should treat disagreement as a source of doubt; if the atheists are clearly much less biased, then I'm not as sure what to think. Here's one reason to take disagreement seriously in cases of universal bias among experts: It's good reason, prima facie, to think that *you* might be biased too.

Angra Mainyu said...


Good point. In the case in which all experts are heavily biased, there is the issue of whether the person making the evaluations is biased as well. However, in that case, rather than giving weight to heavily biased opinions, I would say that she should make sure she's not biased, and if she finds that her assessments were the result of bias, then reassess the matter, without bias.
Now, if that's not psychologically possible for her, that seems to lead to some unusual questions, like: What should an agent who is invincibly irrational when assessing a matter do, in order to assess the matter? But in a sense, that sounds like a question of how an agent that is incapable of acting as she should, should act?
I guess a way out would be that maybe she can rationally think about thinking about the matter in question, even if she [psychologically] cannot rationally think about it directly. So, what should she do?
I recognize I do not know, but I don't find it intuitive that she should give some weigh to the opinions of other people who aren't thinking clearly, either.
If she really can't help it, maybe she should just drop the issue...but I'm not sure agents are so invincibly irrational. If she were to make a conscious, sustained effort, wouldn't she have a shot at being able to properly assess the matter?

Daniel Toker said...

Appropriately, Adam Elga was my undergraduate advisor. He "agreed to disagree" with my thesis on the metaphysics of mind (I did very well despite his disagreement).

Chaoticia said...

In my opinion and interest in Advaita Vedanta, advanced "transcendental", "spiritual", or meditative states are related to phosphenes or inner light visualization and/or quiet identification to the perception of anything that comes across as impersonal or other than the normal perception of the body. Of course from my view, this doesn't prove theism or anything else supernatural, its just the mechanics of these states.

Yet there is still the mysterious ability of thought in waking consciousness, especially linguistic thought, to appear like the pop-ups in a pop-up book, a little similar to how the five bodily senses cause the body to feel separate from the world.