Kripke in ‘Heat’

I want to pick up on some points that Danny was bringing up in his last post…

To pit the relevant points against each other, Kripke’s attack is on the claim that, ‘consciousness is a brain process’, is a contingent identity statement. For the ID theorist, I guess, this kind of identity is desirable because it allows for a the conceptual independence of relata that are ontologically identical. This way the layman can talk about lightning without knowing anything about electric discharge, heat without knowing anything about molecules, and pain without knowing anything about neuroscience. This seems to be Place's antidote to dualist arguments resting on an insistence of the ontological independence of reference for distinct concepts.

Now embark an experiment in thought with Kripke guiding. We should entertain the question along the way as to whether Kripke is begging the question against ID by assuming that conceptual distinctions belie ontological ones. I find the experiment unconvincing, and I’d like to hear some input about whether or not I’ve got it right and why it has had so much pull for folks.

Imagine a population of Martians who feel ‘heat’ when they touch ice, or any other solid with exceptionally slow molecular motion and feel ‘cold’ when they touch fire, and other objects where there’s lots of molecular agitation. I think we can imagine this situation. Given the conceptual distinction here, are we entitled to say that ‘heat is the motion of molecules’ is a true identity statement of sorts? The ID guys say yes, but it’s a contingent identity; Kripke says yes, but it’s a necessary identity: the conceptual distinction we think we see isn't really there.

On Kripke's account, we just first say, yes, it’s just that Martian ‘heat’ is cold and Martian ‘cold’ is heat. But, of course, we aren’t talking about terms here, not about what Martians would say in martianese or in what they would say in English if they new it, when having a particular kind of experience. We’re talking about sensations, and Kripke invites (implores?) us to join him in the intuition that, even were there no creatures to feel ‘heat’, heat would still be identical with the motion of molecules. But this is altogether less obvious. If anything, if we are wont to award some pull to Kripke’s imagination, he seems to be readable as giving an argument for the non-identity of reference for our concepts of HEAT and MOTION OF MOLECULES.

For instance, where there are no creatures to sense ‘heat’, one might also be pulled to say that, sure, there might exist the motion of molecules, but that needn’t be identical with ‘heat’ as we know it. This is plausible if we allow imaginary things like Martians who feel ‘cold’ where we feel ‘heat’. The sensations themselves, as Kripke points out, are contingent. But there is no argument here that the sensation of ‘heat’ is essential to the motion of molecules, in fact, just the opposite seems to be supported. If we disallow contingent identity, we might wonder whether we have an identity statement here at all. All things being equal, functionalism is looking more and more attractive. If we allow that the motion of molecules might produce a different sensation in an exotic kind of ‘nervous system’, why assume that ‘heat’ is identical to the motion of molecules just because we sense it that way?

But it is worth noting that Kripke completely side-steps what Place and Smart have in mind: that sensations of ‘heat’ might be brain processes. Leaving this as an empirical hypothesis, there is room to say that other kinds of brains (maybe Martian brains) might sense the motion of molecules as ‘cold’. But this is either just a defense of the contingent identity holding between the referents of ‘heat’ and ‘motion of molecules’, or it’s an argument for the non-identity of these relata. But Kripke advocates neither.

Nevertheless, Kripke continues along this questionable line, taking it as a given that heat and the motion of molecules are the same thing (and necessarily so). What if there were no creatures initially, then some evolve, like the Martians, that sense what we call ‘heat’ as cold? Again, here, Kripke explicitly assumes the objectivity of the property of being hot and it’s identification with the motion of molecules. ‘Would we say,’ he asks, ‘that heat has suddenly turned to cold?’ No, he says, instead we’d say that Martians didn’t feel ‘heat’ when we do. But this seems to beg the question and to fail to address the issue of the phenomenological fallacy. We might say, to be more careful, that the Martians feel the motion of molecules differently. This, to some extent incompatible with Kripke's intuition that HEAT is the MOTION OF MOLECULES.

The problem I suspect is an equivocation on the sensation of heat and a theoretical conception of HEAT. At all events, the situation is markedly less clear when we substitute the identical predicates, ‘agitation of molecules’ and ‘slowing down of molecular motion’ for heat and cold respectively. We should say, then, that the new creatures sense heat when molecules slow down and cold when they’re agitated, and then contingent identity is confirmed, unless we presuppose that heat just is the motion of molecules. But the support for this presumption was not strong.

In effect, there is an important sense in which Kripke and the classical ID theorist might be talking past each other: heat is not, and should not be identified with the motion of ‘external’ molecules. Rather, if I can pretend I’m an ID theorist, ‘heat’ is just a sensation, and so a property of the nervous system; do we have any independent evidence otherwise? As the thought experiment shows, maybe the sensation of ‘heat’ should just be identified with contingent brain processes. So it might be the motion of molecules, but not anywhere else but in a nervous system appropriately composed.

All this may just point to a categorical difference between ‘simple’ sensations like heat, pain, taste, etc. on the one hand and those which are annexed to concepts like LIGHTNING, or LIGHT, and even HEAT, in there theoretical senses, on the other. If we avoid the phenomenological fallacy, by saying that heat is no property of an experience (no property of the world outside nervous systems; which is not to say that it is a property of an experience in a phenomenal field), and that the visual experience of lightning is the same, etc., the question becomes whether we are miss identifying 'heat' with the motion of molecules in objects outside the nervous system. But I don't think this is a real worry; we're after contingent identity after all, and we can tell some story about how processes in the nervous system are causally correlated with the motion of molecules in objects, we get contingent identity, of sorts. Maybe, this is a little daunting, and I’m not sure where it leads; without a broader metaphysical realism it might appear to problematic, but this wouldn’t concern Place who explicitly advances a scientific hypothesis.

I’ll wind it up by saying that the analogy with mind-body identity is correspondingly weak here. With regard to Kripke’s argument, I don’t see an obvious reason why we can’t treat PAIN like HEAT, at least tentatively. Kripke says we pick out heat by the contingent fact that it affects us in a particular way, but isn’t this the case with pain as well? With 'heat we just have the further consideration of the correlation between neural states and molecular states in objects; with 'pain' we're concerned with neural states only; but neither need involve an irreducible phenomenological story. This is why I suggest that Kripke equivocates on two senses of ‘heat’. The sensation of heat could be contingently identical to brain processes and the motion of molecules in objects; the important thing is that that would not entail that our sensation of heat is not identical to molecular motion. We have ‘heat’ our sensation, which is contingently identical to the motion of molecules in nervous systems, and 'heat' independently understood as the external motion of molecules. Both are independently verifiable, but one is a property of molecules in external objects and one (according to Place) would be a property of a brain process. But we needn't defer immediately to the phenomenological fallacy. If the ID theorist is right, then the 'external' vs 'introspective' distinction is misguided (at least in some cases) to begin with. If so, contingent identity by composition is alive.