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Here is a quick puzzle about the neurological dependence of thought that I have spent the morning thinking about. It is often argued that (Cartesian) dualism suffers from an inability to explain why thought seems dependent upon the brain. A sharp blow to P’s head, for example, will usually result in a period of unconsciousness for P.
But is it really the case that one should believe that thought is dependent upon the brain, or upon neurology? After all, the brain’s neurological processes must be sustained by a functioning cardiopulmonary system, and that seems to require that, at the very least, it would be the whole organism upon which thought is dependent.
And this is where the fun begins because this is where we have to ask whether the dependence relation at play in the objection is necessarily transitive or whether there are some sui generis self-dependent entities. If the dependence relation is transitive, you get (by my lights) humorously counterintuitive possibilities, such as:
1) If thought is neurologically dependent and neurology is cardiopulmonarily dependent, then thought is cardiopulmonarily dependent.
2) If thought is cardiopulmonarily dependent and the cardiopulmonary system is dependent on breathable oxygen, then thought is dependent on breathable oxygen.
3) If thought is dependent on breathable oxygen and the presence of breathable oxygen depends on Earth’s distance from the sun, then thought depends on Earth’s distance from the sun.
4) If thought depends on Earth’s distance from the Sun and Earth’s distance from the Sun depends on a region of empty space between Earth and the Sun, then thought depends on a region of empty space between the Earth and Sun.
5) If thought depends on a region of empty space between Earth and the Sun and any region of empty space is a void, then thought depends upon a void.
I am not sure what to make of this sort of chain of inference, but you can have fun constructing your own. I suppose the question for those who believe that thought is neurologically dependent is, why stop at neurological dependence, why not push for the view that each thought in each of our heads depends upon our entire universe?
Sunday, August 3, 2008
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7 comments:
Of course, we need to differentiate between constitutive dependence and side-constraints. It seems, to me at least, that the dependence of thought on neural activity is difference from the dependence of neural activity on the right mixture of blood and oxygen.
It's a contingent fact about the presence of oxygen in our atmosphere that the Earth is 300million miles from the sun, and there are certainly other conditions under which an atmosphere could have the appropriate mix of oxygen, nitrogen, etc. Plus, there's those handy little astronaut suits, into which oxygen can be pumped. Point being, it's a bit misleading to say, in any strict sense, that "the presence of breathable oxygen depends on the Earth's distance from the Sun."
Plus, we could run this same line of argument, in theory, against the claim that neuroactivity is dependent upon a cardiopulmonary system. We're all familiar with the Brain-in-a-vat thought experiments, wherein the functions usually subserved by the cardiopulmonary, PNS, spinal cord, etc. are instead carried out by tubes, wires, etc. In order to even get your reductio off the ground, I think you almost have to be committed to the conceptually impossibility/implausibility of BIV scenarios. Good luck arguing that point.
What I think is important to this discussion is the imaginative resistance that some/many run into when we try to carry BIV-type scenarios even further. For instance, not everyone thinks we can preserve thoughts by replacing individual neurons with functionally-equivalent microchips. Hard-core functionalists tend to have no problem with such a thought experiment, since they tend to care more about the functional role being served (e.g., processing electrical stimuli)and less about the thing subserving the functional role (i.e., gray matter neurons vs. silicone microchips). Ironically, your argument seems to suggest the same result: if thought isn't dependent on neurology, then switching out neurons with microchips shouldn't make a difference. But this might lead to some pretty counter-intuitive implications, too (at least, counter-intuitive to substance dualists, I suspect). You tell me.
For the record, extended mind theorists run a pretty similar line of argument as what you've got here, only their point is that there's no principled reason to limit cognition to the brain (or, further, to the individual). The result of their argument is that we have reason to think that multiple individuals (acting as a sort of dynamical system) can all participate in one 'mind'. I wonder if this is another unfortunate consequence (for the dualist) of your line of reasoning...
Adam, you rascal. Always ready to pounce on the language where you see a weakness.
This is mere wordplay. "Dependence" is being played like the ambiguous fiddle it is. Distinguish two kinds of dependence - constitutive and provisional. X depends constitutively on Y if Y is a part of X. X depends provisionally on Y if Y is not a part of X, but Y enables X to exist. It's the difference between "the sidewalk depends on the concrete" and "the sidewalk depends on the Street Bureau". Consciousness constitutively depends on neurology, not on millions of miles of empty space. N'est pas?
Two things:
First, you need to show that the dependence you are referring to is necessary dependence. Are any of these things necessary for thought?
Second, with regard to 4 and 5, it is a huge leap (and I think a huge mistake) to equivocate between 'empty space' and 'void'. These are different.
Do you think that these chains of inference are really a convincing problem for people who argue that consciousness constitutively depends on neurology?
JD, I think Adam just assumes necessary dependence. Those who think that there is neurological dependence of thought think that yes, it is precisely as you say "necessary for thought".
Also, I agree that voids and empty space are probably different in important ways, but how is the distinction you make here "a huge mistake" to Adam's argument, that these odd inferences seem to persist given the commitment that thought has some kind of neurological dependence?
Good discussion everyone! Let me respond to some points in reverse order.
**Wes asks: Do you think that these chains of inference are really a convincing problem for people who argue that consciousness constitutively depends on neurology?
I answer, it depends on the picture of thought that the materialist wishes to defend. At the very least, such considerations should persuade those materialists who argue that the subject of thought is the human animal (Olsen, Van Inwagen, Hershenov, et. al) to rethink their position.
**Justin asks: with regard to 4 and 5, it is a huge leap (and I think a huge mistake) to equivocate between 'empty space' and 'void'. These are different.
I answer, it is a leap, and probably mistaken. I should have pushed a different and more absurd endpoint. I am fairly certain that with reflection one could be found.
**Bill asks: Consciousness constitutively depends on neurology, not on millions of miles of empty space. N'est pas?
I answer, Bill you old Armstrongian you! Seriously, if a token thought is taken to be an item supervening on the non-conscious states of affairs of the world (and thus adding nothing to being), then why shouldn’t it be supervening on ALL of the states of affairs?
One point (maybe the only one) to draw from the foregoing is that there is no principled place to draw the distinction between the merely provisionally dependent and the constituitively dependent.
Finally, I answer (the other) Adam: As far as BIV objections go, the above was just intended to bracket such concerns. Surely those who raise the NDT objection to dualism must already bracket the BIV scenario, on pain of absurdity. As far as microchip replacement of neurology goes, I am less certain than perhaps other dualists would be about the chances for success. A brain is (by my lights) an object with a very complex dispositional makeup, and a soul is (by my lights) an object with an equally complex dispositional makeup, there is no telling (short of empirical testing) how neuron replacement would affect the reciprocal relation between brains and souls. Lastly I think there is a principled reason to limit cognition to the brain insofar as my phenomenal awareness of myself qua subject of thought extends no further.
Adam,
**such considerations should persuade those materialists who argue that the subject of thought is the human animal to rethink their position.
Woh, why? I'm not convinced!
I agree (I know you weren't really making this point) that there is an important scientific lesson here, that it is probably a mistake to think about bits of an organism removed from its proper context in that organism, especially really complex ones. So while it sounds a bit silly to say that neuro depends on x that depends on y that depends on the cardiovascular system (and the things that support it)......of course it does! The distinction between these systems are made to serve important pedagogical tools, but the blind separation of these things sort of reminds me of that spiny game you play when you are a kid where you have to match barnyard animal sounds with the animals who make them (eg. thought is the sound that the brain makes). This account is just entirely too simplistic.
You no doubt agree since your inferences in 1-2 are about just this sort of fact that the brain is supported by other internal mechanisms and those mechanisms in turn have needs. That seems less silly somehow then the claim that thought depends on the void at least. And I think that the materialist would be glad to give you lots of physical explanations for all of this. However, there's something weird going on between 1-2 and 3-5. I would speculate, as other have, that that weird thing is an obvious ambiguity with the word 'depends' and your formulation of the relations.
Technically, at least according to Lewis, causal dependence is not a transitive relation, and causation between events does not necessarily imply causal dependence. I guess what I'm getting at is that maybe you're right and there is some crazy causation between 'the region of empty space and the sun' and thought, but that doesn't have to give us causal dependence between those two things. Not a big deal, just formulate it another way.
So, can you formulate the chain of inference you make from thought to void in 1-5 using a more precise causal language?
That might make the argument more convincing. I think the reason why I am not convinced yet is that once you do that, all of this will seem like a squabble about language or concepts and not really anything about the brain.
The first dependency relationship (thought dependency on neurology) is to be understood both as "can be affected by" and "is implemented in", while the last 3-4 steps of dependency are just of the latter type. So no, "dependency" is not transitive because we have different meanings of this word in each step.
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