N = a particular neural state
P = a particular pain
W = a particular wince
Jaegwon Kim says that it's a particular neural state (N) which is the “supervenience base” of my toothache.
Thus what if I winced (W) from my pain (P)? What would have caused that wince? Surely it must have been the pain that caused me to wince. Kim, on the other hand, believes that it's a particular neural state that caused me to wince. Or, as Kim himself puts it, N is “causally sufficient for wincing”.
Is there a difference between N and the mental experience of the pain? If N and P are two different things, then both N and P might have caused me to wince. However, according to Kim, this would be a case of something being “causally overdetermined”.
Why does it automatically follow that if two things cause a third thing that this third thing is causally overdetermined? It may take two or more things to cause a third thing. Actually, there can be many causal conditions which are required to bring about a particular effect.
Of course overdetermination has been widely discussed in philosophy. (E.g., in the ontology of objects and in the philosophy of science.) However, Kim doesn't got into detail in the papers I've consulted. The following is probably the reason why.
If P and N are one and the same thing, then to say that both P and N (as separate phenomena) cause W is a case of overdetermination because they're the same thing. Though that's not really causal overdetermination: it's thinking that one thing is two things. Thus, in actual fact, there's no genuine overdetermination.
In any case, there's an alternative to this possible overdetermination which involves a three-way journey from N to the wincing.
We can have a chain from N to P to W. Yet Kim says that N and P are perfectly simultaneous. There's no causal journey from N to P because they occur at one and the same time....Do they? It's indeed the case that human cognition can't register the time-lapse between N and P; though that doesn't mean that there is no time-lapse. The interval might have been milliseconds. And even if only a millisecond, that would still have constituted a temporal and "causal gap" between N and P.
Kim completely rejects this causal gap. Indeed he doesn't even discuss the possibility that it may exist. Instead he says that P “supervenes on” (or is “realised by”) N: it's “not caused by it”.
Thus supervenience isn't a relation of causation. When we say that P supervenes on N, that doesn't mean that N causes P. It means that P simply supervenes on N... Though what exactly does that mean?
Can such supervenience occur without causation? If it does, then how and why is that the case? And if this applies to the relation between N and P, does it also apply to all mental states and their supervenience-bases?
For example, say I form a mental image of David Cameron. That means that I can't say that neural or brain state N causes my mental image of Cameron. All I can say is that the mental image supervenes on a particular neural/brain state. Though, again, what exactly does that mean?
What is the Causal Role of Pain?
So what had the main “causal role” in my wincing? Was it N or P?
If N doesn't cause P (i.e., P supervenes on N), then perhaps that question doesn't make sense. Perhaps both N and P caused W. Though Kim has just said that this is a case of overdetermination. If that's the case, then wouldn't that mean, surely, that Kim wants to get rid of either N or P?
Kim can't get rid of N because there'd be no pain without a neural state. So can he get rid of the pain itself? Surely not. Would I have winced without a (mental) pain? Of course not... surely.
Kim, at a prima facie level, does seem to want to get rid of P. Or at least he writes that “if we trace the causal chain backward from the wincing, we are likely to reach N first, not the pain”. Indeed he continues by saying that it's
“incoherent to think that the pain somehow directly, without an intervening chain of physiological processes, acted on certain muscles, causing them to contract; that would be telekinesis, a strange form of action at a distance!”.
This seems to be a denial that the purely mental can act on the physical. Or, at the least, that the mental can only act on the physical if the mental itself is physical. (Or if it, in this case, supervenes on the physical.) That would be the Cartesian or dualist position which Kim rejects. Indeed something purely mental acting on the physical (in this case, on muscles) would be like “telekinesis” or “action at a distance”. I suppose this is a reference to a presupposed (metaphorical?) distance between the pain (qua purely mental) and the physical. The only way out of that would be to see the mental and physical as one – otherwise we would have telekinesis or action at a distance.
Kim, of course, doesn't reject either pain or the mental generally. Instead he says that “if the pain is to have a causal role, it must somehow ride piggyback on the causal chain from N to the wincing”. (We'll need to discover what exactly “pain riding piggyback on N” actually means.)
As stated, Kim firmly rejects what he called the overdetermination that is “two independent causal paths”. That would be one from N to the wincing and the other from the pain to the wincing”. The simple way out is to see N and P as one. Though how can a neural state and pain be as one? That was the question that was asked by old-style identity theorists as well as by dualists. The only difference here, it seems, is the introduction of the notion of supervenience. Though is that notion satisfactory and/or acceptable?
Is Pain Epiphenomenal?
The obvious conclusion to all this is to say that P is epiphenomenal. And that's what Kim does seem to say.
So is there a difference between the following? -
P supervenes on N.
P is epiphenomenal.
In other words, if P is truly epiphenomenal, then it “is wrong to think of pain as a causal effect of N”. In the end, then, a question has to be asked: What purpose does P serve?
In fact earlier in the paper Kim himself cites an analogical case. In this example he refers to the shadows of a moving car. He writes:
“The shadows are caused by the moving car but have no effect on the car's motion. Nor are the shadows at different instants causally connected...”
And then Kim compares the car's shadows with someone's toothache. He writes:
“Similarly, you may think that the pain in your tooth has caused your desire to take aspirin, but that, according to epiphenomenalism, would be a mistake: Your toothache and your desire for aspirin are both caused by brain events, which themselves may be causally connected, but the two mental events are not related as cause to effect any more than two successive car shadows.”
Again we can ask: If all that's the case, then what purpose does the pain serve? After all, according to Kim, it's
“[b]eing real and having causal powers go hand in hand; to deprive the mental of causal potency is in effect to deprive it of its reality”.
(The problems with that view is that it would also make numbers, past events, propositions, etc. unreal.)
Indeed without the pain working as a genuine cause, aren't we talking here about a simple mechanical cause and effect without the interaction of any kind of mentality? If the toothache, in this instance, has no causal role, then what role does it have?
Reductionism or Eliminativism?
Kim's solution to all this seems to be old-style reductionism. Or at least he puts the reductionist position when he says that the “reductionist identifies pain with neural state N”.
Indeed in another paper Kim does argue that pain as a "scientific kind... must go” and that elimination or reduction is the answer. That's primarily because - in Kim's case at least - of the problems associated with the multiple realisability of mental kinds in many and various physical substrates.
Although I won't go into detail on this, this is what Kim himself writes on this subject:
“.... the frank acknowledgement that MR [multiple realisability] leads to the conclusion that pain as a property or kind must go. Local reduction after all is reduction, and to be reduced is to be eliminated as an independent entity.”
As I said, it's clear that Kim accepts that pain and mental states/qualities exist: it's just that they aren't deemed to be scientific kinds or properties.
However, when putting the case for supervenience, Kim also identified P with N with the addition of supervenience. Unless, of course, such a reduction can exist side-by-side with supervenience.
In any case, Kim happily finishes off by saying that
“reductionism has been rejected by the majority of philosophers of mind for what they take to be compelling reasons”.
Kim, Jaegwon, 'Multiple realization and the metaphysics of reduction' (1992)- 'Mental Causation' (chapter 6) in his Philosophy of Mind (1996)