If Dr. Ryan is right, then I am wrong. So I am 'forced' to look into this matter. My comments are in italics.
Consciousness (i.e., all mental states) is just states of the brain, functional states, like software being run, but nevertheless physical like software, rather than non-physical. The program running your web browser right now is physical, and, by the same token, so is the consciousness in your brain. Here's why.
A minor cavil: hardware, and the brain's 'wetware,' are undoubtedly physical, but software? The implementation of a program — the 'running' of it on a machine — is physical, but the software itself is arguably abstract. But I won't pursue this line because it is tangential to my main concern.
If consciousness were non-physical, we could conceive of a physical, human body operating normally, exhibiting the behavioral and brain states of a normal person but being devoid of any consciousness. "Hello," it might say, as it smiled and shook your hand, with the lights on but nobody home. In other words, if consciousness were non-physical, it could be peeled away from the brain in a thought experiment such as this. We could conceive of the brain working its neural net as usual but without any consciousness being generated by its activities. Such a being we could call a "zombie," but it wouldn't be like the zombies in the movies who act sleepy. Ex hypothesi it would act just like you and I.
This is all boilerplate in contemporary philosophy of mind. The problem is the whole field zigs where it should zag. It accepts that zombies are conceivable and then either tries to squirm out of the resultant dualism somehow or just gives up and accepts dualism. But we cannot conceive of zombies.
Jim's main argument is an instance of Modus Tollens:
1. If consciousness were non-physical, then zombies would be conceivable.
2. Zombies are not conceivable.
Therefore
3. Consciousness is physical.
Ryan now supports premise (2):
To conceive of a kind of thing requires that one have an idea of what would count as evidence that there was a thing of that kind. To understand "apple" requires knowing what counts as evidence that there is an apple on the table, for example. But no one has any idea what would count as evidence that someone was a zombie. Look into its eyes, shake the hand, but, try as you might, you have in principle no way of telling that your new acquaintance is a zombie. Does he not cry when hurt? Does he not swoon during courtship? Ex hypothesi he does. So, the concept of "zombie" is meaningless. The word "zombie" is as meaningless as "round square". Therefore, "consciousness is non-physical" is incoherent.
Granted, nothing could count as (objective, third-person) evidence that a person is a zombie. But it is equally true that nothing could count as (objective, third-person) evidence that a person is not a zombie. Therefore, if Ryan infers that the concept zombie is meaningless from the fact that nothing could count as evidence for zombiehood, then he also ought to infer that the concept conscious being is meaningless from the fact that nothing could count as evidence for someone's being a conscious being.
So Ryan's argument is sound if and only if the following parody argument is sound:
1*. If consciousness were physical, then conscious physical beings would be conceivable.
2.* Conscious physical beings are not conceivable.
Therefore
3.* Consciousness is not physical.
This proves that consciousness is nothing more than synapses firing. It is inconceivable that mind and body exist separately.
It proves nothing of the kind since my parody argument completely neutralizes Ryan's argument.
But let's take a step further. Ryan says that nothing could count as evidence that someone is a zombie. Well, I have excellent (subjective, first-person) evidence that I am not a zombie. (I pinch my arm and I feel something.) Since I know that I am not a zombie, it is true that I am not a zombie. Therefore, the proposition I am not a zombie is meaningful. (Meaningfulness is a necessary condition of having a truth-value.) But this proposition cannot be meaningful unless the concept zombie is meaningful. Therefore, the concept zombie is meaningful. The fact that there can be no objective third-person evidence that anyone is not a zombie has no tendency to show that the concept zombie is meaningless.
Another reason to think it meaningful is the fact that solipsism is conceivable. I know that I am conscious, but I have no evidence that the rest of you are. You people who comment on my posts — you could be just a bunch of robots. The Big Ho is just a Big Bot for all I know. It would be interesting to compare Ryan's naturalism with Dennett's. But I'll leave that for later.
Nice use of the pragmatic maxim. I fully agree with this line of reasoning.
Posted by: Clark Goble | Monday, 30 May 2005 at 21:44
Just to add one brief comment, I tend to think that the whole Zombie issue is just the old "problem of other minds" wrapped up so as to appear to be something difference. Dressing up a classic problem often obscures what is interesting about the original problem. I think the real issue is simply how we can tell whether other people have minds like ourselves.
Posted by: Clark Goble | Monday, 30 May 2005 at 21:46
Hi, Bill. Good work. Two points. Your argument that "zombie" is meaningful because you know you are not a zombie isn't sound. It would also give you that "shmungie" is meaningful since "shmungie" is defined as "bazungy and not conscious." The fact that you know you are conscious gives you no license to claim that you are not shmungy. You rather have to say, "I know I'm conscious, but "shmungie" means nothing, so I can't tell you that I'm not that. If you decide to define it as "functionally just like me but not conscious" then I don't follow the idea. If you go for "functionally just like a rock and not conscious," then okay, I'm not shmungy. It depends on what you decide "bazungy" means. The argument about consciousness being meaningful is intriguing but incomplete. At this point, I'd say that since you know you're conscious for a variety of obvious reasons (sensations, for example), you know it isn't the case that you are not conscious. You could have evidence that you were not conscious after you regain consciousness. You can have evidence that rocks and sleeping people are not conscious (behavioral and neurological evidence). As for Dennett, in the grad school I went to we were led to believe that he just wasn't serious enough, that he simply wouldn't say whether he was an eliminativist or not. ("Well, if you take an intentional stance then X. But if you take another stance, then Y.") Years later I rethink that and wish I had time to reread his books. I'm a functionalist. If Dennett is not, then he and I don't agree. Thanks for a fascinating post. I'll check back to see where your thinking develops. Clark, I'm trying to adhere to the pragmantic maxim.
Posted by: Jim Ryan | Wednesday, 01 June 2005 at 18:56
Jim, It's funny how you and I can so thoroughly agree politically while differing so wildly on questions of metaethics and metaphysics, differences which appear rooted in different views about truth and meaning. You are right that the fact that I am conscious gives me no reason to conclude that I am not schmungy. But that is only because 'schmungy' is defined in terms of 'bazungy,' a term to which no meaning has been assigned. You say the concept zombie is meaningless. I don't get it. Of course, I cannot know that my wife is not a zombie, but I do know that I am not. Therefore, the concept zombie is perfectly intelligible (understandable): I know that I do not fall under it, and I know that I cannot claim to know that my wife does not fall under it. How would that be possible if the concept zombie were meaningless? Indeed, that the concept is meaningful is proven by the fact that you claim it to be meaningless. Compare 1. Zombie is meaningless. 2. Bazungy is meaningless. (1) is false while (2) is true. If you say they are in the same logical boat, then I say you have dug your hole deeper still -- if you will forgive the mixed metaphor. Thanks for commenting, and I hope we don't lose you entirely to the business world.
Posted by: Bill Vallicella | Wednesday, 01 June 2005 at 20:09
Clark, What do you take to be the pragmatic maxim? Not clear to me how I apply it. I should think that a pragmatist would be more likely to take Jim's side of the argument.
Posted by: Bill Vallicella | Wednesday, 01 June 2005 at 20:11