Saturday, September 09, 2006

Bridging the gap

In this interesting paper, Peter Carruthers and Elizabeth Schechter (‘C & S’) argue that the case for panpsychism expounded by Galen Strawson (previously discussed here and here in this blog) fails to close the explanatory gap “between description of the physical and functional properties of the human body and brain, on the one hand, and consciousness described in phenomenal and experiential terms on the other”.

C & S claim that “even in a best-case scenario—in which the phenomenal properties of the ultimates are known in complete detail—panpsychism still wouldn’t help us with the mind/body problem”. That is, they argue that even on the assumption that the ultimate constituents of matter are experiential and that we have complete knowledge of this experientiality, no gain is made in explaining the relation between this microexperientiality and human consciousness (henceforth referred to as ‘macroexperientiality’).

In support of this stance, the first argument C & S make is a corollary of the zombie argument against physicalism: “couldn’t there be someone who was composed of particles exactly like mine arranged in exactly the same way, each of which possessed the very same qualia as do the particles that compose me, yet who lacked phenomenal consciousness altogether”.

Given that current state of knowledge of microexperientiality (or lack thereof), the conceivability of zombies if microexperientiality obtained is hard to dispute. However, C&S' much stronger claim is that even if we had a complete knowledge of microexperientiality, it would still be conceivable that macroexperientiality didn’t exist, “[in] which case no amount of knowledge of the feely nature of the ultimate physical particles could ever explain phenomenal consciousness, in the way that knowledge of the component particles of water and the manner in which they interact can explain liquidity.”

The claim here is that macroexperientiality cannot be reductively explained in terms of microexperientiality in the same way that consciousness, at least in the view of some, cannot be explained reductively in terms of physicalism (where reductive explanation entails that an appropriate account of lower level processes will, in principle, automatically lead to explanation of higher level phenomena).

I do not think there is an equivalence between these two scenarios. Whilst it may indeed be conceivable that a complete knowledge of physics will never yield an explanation of consciousness, we don’t know whether it is conceivable that a complete knowledge of microexperientiality would not necessarily yield such an explanation. There is in fact no reason to believe macroexperientiality could not be reductively explained in terms of microexperientiality, because we simply don’t know enough about microexperientiality to make such a claim. It may be the case that a complete knowledge of microexperientiality would mean that an explanation of macroexperientiality would automatically follow in the same way that knowledge of the behaviour of the constituent particles of water explains it’s liquidity.

Thus, there is an epistemic asymmetry between the capacity of consciousness to be reductively explained in terms of physicalism on the one hand and microexperientiality on the other. Not knowing whether microexperientiality could give rise to macroexperientiality is not the same as knowing the physical could not give rise to the experiential.

C & S partially address the above objection in addressing a possible response to their argument: “Since we cannot really conceive, in detail, of millions and millions of experiential entities interacting in as-yet-to-be-specified and highly complex ways, we cannot really tell whether some such story mightn’t constitute a successful reductive explanation of our own experientiality”. The rejoinder of C&S to this is that “But this sort of reply is equally available to defenders of standard (non-experiential) forms of physicalism, of course (Dennett, 1991). So if it works, it would only serve to undermine Strawson’s own argument for panpsychism.”

However, I think it is doubtful whether these two solutions are “equally available”. The problem of the generation of the experiential from the physical is that of how physical predicates could lead to an explanation of experiential predicates, and the apparent lack of any explanatory connection between the two levels of description. But these limitations may not apply in the derivation of macroexperientiality from microexperientiality: the problem in this case is one of how something more complex arises from something simpler but of the same type, not of how something qualitatively and ontologically new arises from something of an entirely different nature. Thus, there is a lot less required to get from microexperientialism to macroexperientialism than from standard physicalism to macroexperientialism, so the two are not equally available options.

Another objection that can be made against the position of C&S is that even if it is accepted that macroexperientiality could not be reductively explained in terms of microexperientiality, this does not mean that explanation is impossible - a nonreductive explanation of the former in terms of the latter may be possible. Thus, for example, macroexperientiality could arise from microexperientiality through contingent laws of nature such that macroexperientiality is dependent on microexperientiality without being entailed by it (in the same way that antiphysicalists such as Chalmers contend that consciousness is dependent on the physical without being entailed by the laws of physics). The issue would then be one of what explanatory gain there would be in a non-reductive explanation arising from microexperiential ultimates as opposed to non-experiential ultimates (an issue which I discussed in the post previously linked).

One of the final points that C&S make is that the fact that microexperientiality is of the same metaphysical type of macroexperientiality does not procure any advantage in attempting to explain macroexperientiality: “For we have not the faintest idea how the phenomenal properties possessed by one entity or set of entities might contribute to a reductive explanation of the phenomenal properties possessed by another.”

This remark does not account for models have been put forth to explain how macroexperientiality might arise from microexperientiality. To use one example, Whitehead’s metaphysics addresses this issue (although his schema is non- reductive in that occasions of experience have an element of self-determination which is not explicable in terms of lower level experiences, it is equally adaptable to a reductive explanation in which such self-determination is absent). To put it very briefly, Whitehead proposed that occasions of experience of finite temporal duration are constituted largely from prior occasions of experience. Complex experiential occasions arise from synthesis of elements of prior simpler occasions (hence the phrase ‘the many become one and are increased by one’). Thus, under this model a multitude of microexperiential events within the brain could give rise to subsequent more complex experiential events, including what we experience as phenomenal consciousness.

C&S conclude that panpsychism does nothing to close the explanatory gap and that it is therefore preferable to remain a conventional physicalist (they also have their own approach in dissolving the explanatory gap by treating physical and experiential terms as conceptually isolable, which I won’t go into here). However, for the reasons above I do not think they have adequately demonstrated this preference. To recap: Firstly, we don’t know whether there is an explanatory gap between microexperientiality and macroexperientiality in the same way we know the gap exists between the physical and the experiential: secondly, the derivation of the macroexperiential from the microexperiential is less problematic than it’s derivation from the (non-experiential) physical; thirdly, even if microexperientiality could not produce a reductive explanation of macroexperientiality, this does not mean a non-reductive explanation may not be possible and preferable to other non-reductive explanations; and finally, it is not the case that models of how macroexperientiality might arise from microexperientiality are lacking.

So, in my view C & S do not present any strong blows against Strawson’s position that make it inferior to conventional physicalism.

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