As I mentioned in the introduction, the idea from Davidson I’ll be defending in this work is that the mental realm is governed by constitutive principles of rationality, and that from this it follows that mental phenomena have a certain normative character. It’s this normative character which is the basis of my own antireductionism about the mental, not the multiple realizability considerations cited by standard nonreductive physicalists.5 Chapters 2 through 4 will be devoted to working out my nonstandard version of nonreductive physicalism in some detail. Here in Chapter 1, though, I want to start things off by outlining some of the ways in which my position diverges from Davidson’s. Davidson’s view of the mind-body relation, and by extension of how mental causation works, is extremely well known. Also well known are a number of the quite daunting problems his view faces. Here at the outset I hope to head off suspicions that my own position will be subject to the very same problems.
The explicit aim of “Mental Events” is to show how three theses standing in apparent conflict can be reconciled.6 The theses go as follows.
The Principle of Causal Interaction: At least some mental events causally interact with physical events.
The Principle of the Nomological Character of Causality: Where there is causality, there must be a law: events related as cause and effect fall under strict deterministic laws.
The Anomalism of the Mental7: There are no strict deterministic laws on the basis of which mental events can be predicted and explained.
If causal relations are always backed by strict deterministic laws while there aren’t any such psychological laws, then it might seem there can be no mental causation (or, for that matter, any mental effects of causes). This is the apparent conflict. Davidson’s strategy for conflict resolution is to embrace a token identity theory (a.k.a. token physicalism) according to which every mental event token is identical to some physical event token. If mental events just are physical events – that is, if every event with a mental property also has some physical property8 – then causal interactions involving mental events could always be backed by strict deterministic laws, laws pertaining to the physical properties of such events rather than their mental properties. In short, the three theses could all be true. To whatever extent we deem the three theses to be independently plausible, we then face pressure to accept Davidson’s token physicalism. In this way, “Mental Events” provides an argument for physicalism.
1.1 Objections to Davidson’s Argument
I now want to set out a number of objections to the argument just presented. My purpose in going through these objections isn’t necessarily to conclusively refute Davidson. It may be that he could successfully respond to some or all of the objections I raise. Instead, my primary aim is to begin to differentiate my view from Davidson’s: in sections 1.2 through 1.4, we’ll see that the objections laid out here don’t pose even a prima facie problem for my view, as they do for Davidson’s.
The objections I want to consider can be divided into four groups..
1.1.1 OBJECTIONS TO THE TRUTH OF THE ARGUMENT’S PREMISES
As it is initially formulated in “Mental Events,” The Principle of the Nomological Character of Causality rules out the possibility of causal relations backed by indeterministic laws. The actual existence of quantum indeterminacy would seem to offer a fairly compelling reason to reject the principle so stated. Davidson is aware of the potential problem here and responds to it by dropping the requirement that causal relations be backed by deterministic laws. He keeps the requirement that they must be backed by strict laws, though, where at least some indeterministic laws (e.g., quantum mechanical ones) can count as strict. This revision is meant to keep the original spirit behind The Principle of the Nomological Character of Causality in tact – think of being deterministic as a kind of ideal toward which strict laws strive but sometimes fall short.
Once we strike ‘deterministic’ from The Principle of the Nomological Character of Causality, though, we’re also going to have to strike it from The Anomalism of the Mental if the argument for token physicalism is to go through. This move is potentially problematic. For, while it’s fairly uncontroversial that there aren’t any deterministic psychological laws – this is something that’s accepted by a wide range of philosophers of mind who otherwise agree about little – it’s impossible to say how plausible the claim that there are no strict psychological laws is until we know exactly what is meant by ‘strict.’ And, since Davidson’s argument for token physicalism depends on the independent plausibility of his three principles, to whatever extent the revised version of The Anomalism of the Mental is less plausible than the widely accepted unrevised version, his argument will be weakened by the revision.
An account of strictness is needed, then. Davidson’s discussion of homonomic and heteronomic generalizations is meant to gesture at least at such an account,9 though notoriously, the discussion is a bit obscure. Without trying to retrace Davidson’s homonomic/heteronomic distinction or otherwise offering an interpretation of his views on strictness, we can at least say this. However the details of the account of strictness end up going, it will need to satisfy each of the following requirements: (i) it will need to make it plausible that at least some actual indeterministic physical laws get to count as strict – otherwise, the motivation for having revised The Principle of the Nomological Character of Causality will have been lost; (ii) it will need to make it plausible that no true psychological generalizations, not even the extremely robust generalizations discovered in studies on vision or language processing, say, get to count as strict – otherwise The Anomalism of the Mental will be false; and (iii) it will need to make it plausible that the sort of strictness in question is in some sense required for causation, so that there can be no causal interactions which are not backed by strict laws – otherwise, we will have good reason to reject even the revised version of The Principle of the Nomological Character of Causation. Unless Davidson can come up with an account of strictness satisfying each of these three desiderata at once – and I think we ought to be extremely skeptic in advance that he can – he loses his argument for token physicalism.
Moving on, let’s now consider objections which grant Davidson the truth of his three theses but which deny the inference from the theses to the conclusion of token physicalism. Let ectoplasm be a spooky sort of non-physical, non-mental stuff. Nothing in Davidson’s argument rules out the possibility that a property like that of being made of ectoplasm might figure in strict laws.10 But if this possibility has not been ruled out, we do can accept Davidson’s three principles while avoiding his token physicalism. If mental events were token identical to ectoplasmic rather than physical events, and there were strict ectoplasmic laws, then Davidson’s three theses could all be true while token physicalism was false.
Presumably there are good reasons to accept token physicalism rather than this sort of token ectoplasm-ism. Whatever those reasons may be, they don’t emerge from the argument contained in “Mental Events.” And so, if Davidson wants to rule out the token ectoplasm-ism hypothesis, he needs to introduce some further considerations. The problem with this is that these further considerations will then be doing a good portion of the work that any decent argument for physicalism really ought to do on its own. In short: if the argument from “Mental Events” needs to be supplemented in this way to rule out certain anti-physicalist views, then the argument itself must be rather weak.
Ectoplasm can be set aside to raise a related but distinct objection. Davidson operates with an unusual conception of the mental in “Mental Events,” a conception which potentially limits the scope of his token physicalist conclusion. His criterion for mental events goes as follows: an event is mental if and only if it satisfies some predicate that contains a propositional attitude term essentially.11 But then, what about pains, say? If an event e is a pain, then e will satisfy the predicate ‘is a pain.’ Since this predicate contains no propositional attitude term, e’s satisfaction of it doesn’t by itself guarantee that e counts as a mental event.
Davidson recognizes this consequence of his criterion for mental events but thinks that it isn’t genuinely problematic. On a second glance, he says, the worry shouldn’t be that the criterion for mental events is too restrictive; if anything, it’s too liberal. Let e* be an event which is intuitively non-mental, like the collision of two stars in distant space. Now, suppose that e* is simultaneous with Jones noticing that a pencil starts to roll across his desk. Then e* satisfies the predicate, ‘is a collision of two stars and is simultaneous with Jones noticing that a pencil starts to roll across his desk.’ This predicate contains the propositional attitude term ‘noticing’ essentially, and so by Davidson’s criterion, e* counts as a mental event.
But, if the collision of two stars counts as a mental event, then presumably everyevent will count as mental, including the pain e. We can suppose, for instance, that e satisfies ‘is a pain and occurs two seconds after Smith thought that roses are red.’ If so, e counts as a mental event. According to Davidson, the counter-intuitive result that every event is mental is tolerable within the context of his argument: “We can accept Spinozistic extravagance with the mental since accidental inclusions can only strengthen the hypothesis that all mental events are identical with physical events. What would matter would be failure to include bona fide mental events, but of this there seems no danger.”12
There is reason to suspect that this move is too clever by half, though. Davidson’s unusual conception of the mental is meant to be used in understanding the various claims he makes, including The Anomalism of the Mental. Given the conception of the mental that is operative, the Anomalism of the Mental must be interpreted to mean that there are no strict laws pertaining to events insofar as they satisfy a predicate which contains a propositional attitude terms essentially. So understood, the Anomalism of the mental does indeed entail that there are no strict laws governing e insofar as e satisfies the predicate ‘is a pain and occurs two seconds after Smith thought that roses are red,’ but it does not entail that there are no strict laws governing e insofar as e satisfies ‘is a pain.’ But then, for all Davidson’s defense of The Anomalism of the Mental might establish, it cannot establish that there are no strict laws governing e qua pain. If the possibility of such strict laws is not excluded by Davidson’s argument, though, then Davidson has failed to give us a reason to think that e must be a physical event.
This conclusion will generalize to any non-propositional attitude type of mental event. And so, Davidson’s argument for token physicalism provides us with no ammunition to use against an anti-physicalist philosopher who grants that every belief, desire, intention, etc., is identical to some physical event, but who maintains that every pain, afterimage, raw feel, etc., is identical to no physical event.
1.1.3 OBJECTIONS TO THE SIGNIFICANCE OF THE CONCLUSION
Next let’s consider objections that grant the soundness of Davidson’s argument but call into question the significance of its conclusion. In particular, I want to consider doubts as to whether the sort of physicalism Davidson establishes is either necessary or sufficient for physicalism as philosophers have typically understood the notion.
Start with necessity. Some philosophers of mind believe that mental events are constituted by physical events rather than identical to them, in much the same way that some metaphysicians believe that statues are constituted by lumps of clay rather than identical to them. Whatever objections this sort of token constitution thesis might face, it is not naturally classified as a form of anti-physicalism. More generally, it seems to be perfectly possible to be a good physicalist while holding that the determination relation which obtains between mental and physical events is something other than identity.
Now for sufficiency. While Davidson makes a point of noting in “Mental Events” that his token physicalism is consistent with psychophysical supervenience,13 no argument he presents in the paper actually entails the truth of any supervenience thesis. And in fact it’s not obviously incoherent to hold (with Davidson) that every mental event is identical to some physical event while also holding (pace Davidson) that there can be entities that are physically indiscernible but mentally discernible, contradicting all supervenience theses. So, for instance, it’s not obviously incoherent to hold that there are a pair of mental events e and e* which are also physical events and which are physically indiscernible (even when extrinsic physical properties are taken into account) while being mentally discernible. Thus, if psychophysical supervenience is regarded as at least a minimal requirement of standard physicalism, as at usually is, then it appears that the truth of Davidson’s token identity thesis is compatible with the falsity of standard physicalism.
Let me emphasize that the point here is not that Davidson isn’t enough of a physicalist. He, after all, accepts psychophysical supervenience. Rather, the point is that since Davidson’s argument for token physicalism does not by itself seem to entail any supervenience thesis, it does not seem to be properly regarded as an argument for physicalism.
1.1.4 OBJECTIONS TO DAVIDSON’S VIEW OF MENTAL CAUSATION
Finally, let’s consider what are probably the most serious and the most well-known objections to Davidson’s position. Set aside the argument for token physicalism and consider the view of mental causation defended in “Mental Events.” If mental events are identical to causally efficacious physical events, as Davidson holds, then by Leibniz’s Law it follows that mental events are causally efficacious. However, this point by itself doesn’t guarantee that mental events are causally efficacious qua mental – that is, by virtue of their mental properties. And it’s this that seems to be needed to vindicate commonsense and scientific attributions of mental causation.
To take an example from Fred Dretske, imagine a soprano singing the word “shatter” at an extremely high pitch.14 Suppose that the metaphysics of the situation is such that this singing is a single event having two distinct properties: that of meaning shatter and that of being high pitched. Now imagine that the soprano’s singing causes a nearby glass to break. Intuitively, the soprano’s singing being high pitched is causally relevant to the glass breaking in a way that its meaning shatter is not – in fact, the property of meaning shatter seems completely causally irrelevant here.
According to a number of critics, Davidson’s view either entails or at least fails to rule out the possibility that in all cases of causation by mental events, it is only the physical properties and not the mental properties of such events that are causally efficacious. That is, Davidson’s view either entails or at least fails to rule out the possibility that mental events’ mental properties are like the property of meaning shatter in the soprano example, while their physical properties are like the property of being high pitched.15 This is unacceptable. Surely the mental properties of mental events aren’t epiphenomenal in this way. To establish the causal efficacy of mental properties over and above the causal efficacy of token mental events, though, Davidson will need to say more than he does in “Mental Events.”