Comments on "inconceivable"

[Hide] original entry

What odd things some philosophers think. Victor Reppert quotes a book by Edward Feser on the philosophy of mind, which attributes the following argument to W D Hart. (So apparently at least three philosophers take it seriously.)

[...] you can imagine that what you see in the mirror is not even a headless body, but nothing more than the wall behind you and no body at all [...] But seeing is a mental process, as is the frenzied thinking you'd now be engaging in; which means that what you've conceived of is your mind existing apart from a body or brain. So again, it's conceivable that the mind exists apart from the brain -- in which case they are not identical.

Lest there be any doubt about what's being said here, Reppert expands on it in his comments:

If the mind is identical to the brain, then the mind is necessarily identical to the brain. If the conceivability of the mind's existence apart from the brain entails the metaphysical possibility that the mind and brain are not identical, then the mind and brain are non-identical, since identity claims are necessarily true, and their denials necessarily false.

It's a neat trick, isn't it? Let's see what else we can prove this way. I can imagine electric current flowing without any charged particles being involved; therefore electric current is not identical to a flow of charged particles. I can imagine my computer continuing to do its processing without its circuitry and the things that happen therein; therefore what accomplishes my computer's processing is not identical with its circuitry and the things that happen therein.

One might hope that this is only meant to establish that there could be minds that aren't brains; I haven't read Hart or Feser, but Reppert calls it "an argument for dualism". Oh dear oh dear oh dear.

A few other comments: (1) I thought this argument went all the way back to Descartes, but I think Reppert is a Descartes expert and he didn't mention Descartes so it probably doesn't. (2) Reppert's expanded version of the argument is a nice illustration of what a mess the notion of de re necessity can get you into. (3) I am not claiming that the mind is identical to the brain, just pointing out what a silly argument this is. I think it's nearer the mark to say that the mind is an activity of the brain, or a pattern in the brain, or a pattern in the activities of the brain, or something of the sort; if the Hart/Feser/Reppert argument were valid, it would rule those possibilities out too.

On 2007-04-16 at 18:56:06, Gareth Rees said:

Some version of this argument appears to be due to David Chalmers of zombie fame, at least according to Wikipedia. I found Brendan Ritchie's Dualism and the Limits of Conceivability quite amusing: I suspect that these philosophers discussing with all apparent seriousness whether or not "zombie worlds are ideally conceivable" must surely be doing so with tongue in cheek.

On 2007-04-16 at 19:40:58, g said:

There's some discussion by Chalmers himself on You're probably right that the philosophers' tongues are partly in their cheeks, but what I (and no doubt the zombies) would like to know is where their brains are.

On 2007-04-17 at 13:06:57, Gareth Rees said:

That Chalmers paper makes my head hurt, but if I understand it correctly, then he smuggles in his conclusion to the mind-body problem in his first hypothesis (is this standard practice in philosophy?).

Chalmers hypothesises that P&~Q is "ideally primarily positively conceivable", where P is the "conjuction of physical truths about the world", and Q is a "phenomenal truth" such as "someone is conscious". It looks to me as though this is already a claim that Q is not a physical truth (otherwise P would include Q and so P&~Q would be contradictory and so not ideally conceivable). The conclusion that materialism is false would seem to follow immediately.

This seems so bogus that I feel I must have misunderstood some subtlety in the argument...

On 2007-04-17 at 20:53:29, g said:

I agree about the headache-inducing nature of the paper. For me, most of the headache comes from the stuff about primary versus secondary conceivability, which I strongly suspect is more obfuscation than insight.

I *think* some sort of materialism could maybe be true without Q ("someone is conscious") being logically entailed by P (the physical facts). It's hard to be sure, because "conscious" is one of those words that gets used in unclear and inconsistent ways, especially (as it seems to me) by people who want to use it to undermine materialism. But certainly the variety of materialism that I find most congenial says that "X is conscious", when true, is equivalent to some monstrously complicated proposition about X's physical states, so that P&~Q isn't ideally positively conceivable.

More generally, I think that ideal positive conceivability is just enormously difficult to arrange; I'm not even sure anything (including things that are actually true in the real world) is ideally positively conceivable. Chalmers's "arguments" for saying that P&~Q is ideally positively conceivable seem very thin to me, and the way he phrases them makes me think that on some level he realises that too. For instance, "secunda facie conceivability is an extremely good guide to possibility"; well, maybe for easy cases, but it's clear that if P&~Q is impossible then it's impossible for very, very complicated reasons. And "defeating ideal conceivability will require ..."; sorry, Prof C, but I think the onus is on you to *support* the ideal conceivability of P&~Q (or anything else); you don't get to postulate it and demand that others refute it. And I think his claim that "there is good reason to think that [structural or functional] analysis of phenomenal concepts is a misanalysis" comes close to begging the question, too.

On 2007-04-22 at 12:23:18, Gareth Rees said:

I had never realised that there was such a lot of barking mad philosophy devoted to the demolition of naturalism. From C. S. Lewis's argument from reason, to the intelligent designers, to proponents of zombie worlds, to Alvin Plantinga and his "evolutionary argument", they all seem to be of the opinion that armchair reasoning can settle the matter without ever having to look at actual facts.

Is this a sub-branch of Christian apologetics? I can't tell for sure. Plantinga is a apparently a Calvinist.

The intelligent designers in particular seem to be motivated by the desire to replace public school science classes with religious instruction, and they can see that demolishing naturalism is one way to open a crack to let them in.

Still, there are a few moments of humour in the debate. Victor Reppert's reply to Richard Carrier's critique of his (Reppert's) book C.S. Lewis 's Dangerous Idea contains the immortal line:

But with more realistically calibrated requirements for success, perhaps my arguments will turn out a little more successful.

On 2007-04-22 at 15:57:54, g said:

I don't think it's just a sub-branch of Christian apologetics; Chalmers is on record as describing himself as an "absolute atheist". But there does seem to be a sort of cottage industry of philosophy in the service of Christianity, which has produced some extraordinarily silly arguments from the likes of Plantinga, van Inwagen and Swinburne. And indeed Reppert, though he's a relative newcomer to the field rather than an elder statesperson like them.

There's absolutely no question that the ID folks are all about sneaking something like creationism into schools.

Excellent little quotation from Reppert, though in fairness he does seem to be making what might be a reasonable complaint (i.e., that Carrier is making him out to be claiming something much stronger than he really is). But I have neither read Carrier's comments nor looked in detail at his reply to them, so I may be giving him too much credit. (I have read his book, which I didn't find impressive.)

On 2007-05-08 at 03:52:24, Victor Reppert said:

What I actually said was that IF conceivability entails metaphysical possibility, then the fact that I can conceive my mind existing without my brain entails that the two are not identical. I'm not sure what to make of the argument, but it was interesting, and I wanted some responses. Saul Kripke has a very interesting argument for mind-body dualism.

Zombie-type arguments are given by people of all stripes, theistic and non-theistic. Physicalism has critics of various kinds, not just religious believers. Most people think Bertrand Russell was a physicalist, but he wasn't. Thomas Nagel presents the argument from reason against naturalism and then refuses to draw any theistic conclusions from the argument.

As for the claim that people who defend non-empirical arguments against naturalism, the charge seems to be that people like Plantinga and Hasker and myself are using armchair reasoning without looking at the actual facts, I would just point out that this is presupposing that science is going to be a matter of "looking at the facts" without any metaphysical presuppositions. I think it isn't very plausible to suppose this. A lot of people think that inquiry, if it is to be truly scientific, has to presuppose physicalism from the outset. Is the scientific study of mind going to be the attempt to open-mindedly discover whether physicalism is true or not? If you can accuse me of armchair science, I can equally as well accuse people like Daniel Dennett of armchair science as well. If the entire enterprise is conducted with the presupposition that physicalism must be true, why is that any less armchair science than what I am doing? Are the "looks" that neuroscientists are taking really presupposition-free, and do they really answer the philosophical questions, as opposed to presupposing the answer to those philosophical questions.

In my comment in response, I was saying that I was making more modest claims than Carrier was saying that I was. I was trying to show that problems which from a theistic and dualistic perspective could be solved are left mysterious by naturalism. I was not attempting to demonstrate the irrationality of naturalism. I say a good deal about the epistemic status of arguments in the book, which he ignores entirely.

On 2007-05-08 at 10:48:34, g said:

I think it's utterly implausible that conceivability entails metaphysical possibility, but never mind that; the argument, even with that as premise, only works if "identical" implies "not metaphysically-possibly distinct". Is anyone claiming that mind and brain are identical in *that* sense?

I'm not sure that terms such as "physicalist" and "materialist" are useful unless accompanied by more specifics about what the holders of those positions are taken to deny. Denying the existence of numbers, sets and other such abstracta seems to me a very different sort of thing from denying the existence of gods, ghosts, dryads and the like; and both might be quite different from denying the existence of the sort of ground-of-all-being God favoured by some liberal theologians. You mention Russell, for instance; he notoriously changed his mind a lot (but not his brain! aha, a new argument against materialism!) but on the whole his fundamental entities seem to have been, roughly, maximally localized potential experiences. I think he'd have been quite cross to be claimed as an ally in opposing *naturalism*.

Saying "you can't seriously expect to discover the ultimate nature of reality without looking at the facts" doesn't, so far as I can see, presuppose that science should be a matter of "looking at the facts" without any metaphysical presuppositions. The two propositions appear to me entirely separate. (But, for what it's worth, I think well conducted scientific enquiry should try to keep its metaphysical presuppositions minimal, and indeed it generally does.) However, my own main objections to your "argument from reason" aren't to do with "armchair reasoning"; I just think the argument doesn't work, because it assumes a lot of things I see no reason to assume.

On 2007-05-08 at 22:55:25, Victor Reppert said:

I always try to start discussions on the issue of materialism, physicalism, and naturalism by presenting some definitions that I think should be acceptable on all sides. We can start with both materialism and physicalism, according to which

1) Nature, or the physical, is at bottom mechanistic. There are no purposes at the most basic level of analysis. There are no normative truths, the states on that level are describable in third-person terms, in a genuinely physical description of something.

2) The physical is causally closed. If you want to know where a particle will be next week, if you know al the physics (the laws and facts) you have all the relevant causal factors. Nothing about mental states or even biological states is going to help you figure our what's going to happen next.

3) Whatever is not physical, supervenes on the physical. Given he state of the physical, it is not metaphysically possible for other states to be different from what they actually are.

Where does that leave numbers? Well, the trouble here is going to be that if they exist, they can't have anything to do with what causal transactions take place in the world of space and time. So there's going to be a real problem of how it might be possible to refer to them, given a Platonistic view, if we accept something like a causal theory of reference.

As for naturalism, it isn't clear to me that there can be a "nature" that meets all the requirements of one but isn't physical or material. But if there could be, it would be a non-physicalist naturalism, however, if I could get the argument from reason to work against physicalism defined above, I ought to be able to get it to work against naturalisms of other kinds.

Are you with me so far?

A couple of other points: Russell might be quite cross at being appealed to in a critique of naturalism. Searle does get cross (or, as the philosopher's lexicon says, searly) when it is suggested that his arguments have dualist implications if accepted. The question, though, is what the views were and what arguments were used to support them. Argument has a life of its own and turns in directions that those who produce those arguments may not like.

On the non-identity arguments, the identity claim would be that a mental state is identical to a physical state. If such identities hold, it is typically thought that those identities are metaphysically necessary. Hence if it's metaphysically possible that the states are distinct, then the states are distinct, since the identity would not be necessary. Water is H20, for example, is thought to be a necessary truth.

On 2007-05-09 at 02:40:35, g said:

I think your definition of physicalism is OK apart from the fact that it assumes we already know what "nature, or the physical" is. At first sight it looks wrong w.r.t. numbers and other abstracta, but on reflection I think those "vacuously" supervene on the physical: how they are is determined by no-information-at-all, and a fortiori by the state of the physical world. (If there are things like relations between sets of infinite sequences of elementary particles, then whatever truths there might be about those would supervene on the physical.)

I'm not sure how one would go about fitting abstracta into a causal theory of reference; it may be that such a theory begs the question against the possibility of referring to abstracta. If so, so much the worse for causal theories of reference. (Perhaps.)

The notion underlying "naturalism" and "materialism" and "physicalism" and, I think, the notion that the "argument from reason" is most fundamentally deployed against, is something along these lines: "Everything that happens is governed by a combination of determinate law and completely inscrutable chance, and ultimately all explanations can be expressed in terms of those laws and probabilities". But making that rigorous seems to be rather tricky.

As for Russell, Searle and the rest: I wasn't suggesting that anyone gets to legislate on how their positions are allowed to be developed later, or on what subtle implications those positions may turn out to have. But if you want to claim Russell, or Searle, or anyone else, as a "critic of physicalism" -- appropriating, as it were, a little of their status -- then it's *their* positions that matter, not what other people may subsequently have made of their ideas.

And, finally, getting back to the original topic: If that "it is typically thought" is meant to mean that there's a plentiful supply of philosophers who believe in a mind-body identity thesis strong enough to be refuted by the thought experiment, then I'm afraid I just don't believe you. Whether "water is H2O" is a necessary truth, and what it means for it to be one, are of course not matters about which there is anything like universal agreement. Perhaps it would be helpful if instead of "X is thought to be Y" you could say "P thinks that X is Y"?

On 2007-05-09 at 23:45:47, Gareth Rees said:

I see that modern philosophy has added an improved punchline to Francis Bacon's famous parable. We can now have the friars ask if the neophyte's "look" into the horse's mouth was really presupposition-free and whether his "count" really answered the philosophical question or merely presupposed the answer?!

On 2007-05-10 at 10:16:32, Gareth Rees said:

Just to be clear, I think that this kind of philosophical argument about consciousness is a result of our lack of knowledge about the subject.

Today's solid-state physicists, moving individual electrons around, are hardly puzzled by the question of whether they are "really" waves or particles. They're really electrons: there's no need to relate them to some familiar object when they're already familiar from day-to-day experience. I'm confident that tomorrow's quantum computer engineers, working hard to keep their qubits from decohering, will not be troubled by "interpretations" of quantum mechanics. (But they will be able to tell you how long one might, at least in theory, keep Schroedinger's cat in superposition, as a function of the temperature of the box...)

Similarly, I imagine that to a long-future scientist who is familiar with the way consciousness works, and works every day with conscious devices, the zombie arguments will seem amusingly medieval.

For the moment, non-specialists like me can only wait and see. (And poke fun at zombie arguments.)

"[By the 25th century] The problem of the Ghost in the Machine, posed by intellectronics and its thinking computers, could be dealt with more or less [i.e., by modification of religious dogma], but it was followed by other problems, by minds and intelligences in fluids. Sentient, reasoning solutions were synthesized, and these could be bottled, poured, mixed, and after each time you ended up with a personality, one often more spiritual and wise than all the Dichoticians [i.e., mind-brain dualists] put together." (Stanislaw Lem, "The Star Diaries")

On 2007-05-17 at 08:19:25, Victor Reppert said:

Why should we believe that future brain science will vindicate the materialist? Couldn't future brain science go south on the materialist about the mind, in much the way that science went south on believers in universal deterministic causation, or in the way that science went south on the belief in a beginningless universe (though I realize that is somewhat more controversial). It is, after all, FUTURE science.

On 2007-05-17 at 23:11:01, g said:

If I've understood Gareth R. correctly, he isn't claiming to know that future brain science will vindicate the materialist; just saying he expects it to, and positing a certain relationship between science and philosophy.

One reason to expect (not with perfect certainty, of course) that future science will vindicate the materialist on this point is that past science has been pretty good to materialists on similar points.

It doubtless seemed a reasonable idea at one point that life might be incommensurable with mere matter, or at least require some special sort of substance -- "vital spirits" or whatever -- but as we've discovered more about how living things work that's seemed less and less plausible. The idea that mind might be similarly incommensurable with matter seems to me to be some way along a similar path, though there's scope for disagreement about how far.

(Maybe "incommensurable" is a poor choice of word. One could have "life" or "mind" on substrates very different to ours, which amounts to incommensurability of a sort. But the idea that mere material goings-on couldn't *give rise to* life seems handily discredited, and the corresponding idea about mind has been getting steadily less believable with the passing years.)

On 2008-05-03 at 19:53:28, Mark Wainwright said:

You were right about it going back to Descartes; Leibniz's refutation is almost as old:

Someone who thinks that the soul is corporeal ... will admit that you can doubt (as long as you are ignorant of the nature of the soul) whether anything corporeal exists or does not exist. And as you nevertheless see clearly that your soul exists, he will admit that this one thing follows: that you can still doubt whether the soul is corporeal. But no amount of torture can extort anything more from this argument.

"I am amazed that so able a man [as Descartes] could have based so much on so flimsy a sophism", he wrote in the same quote. See

Post a comment:

Name:(will be shown with comment)
Email:(will be kept private)
Web page:(optional; will be linked from your name)
Secret word:(the secret word is two plus two)

You may use Markdown to format your comment, or just include HTML tags. All comments are moderated, so don't waste your time trying to abuse this.