Abstract
The realization relation that allegedly holds between mental and physical properties plays a crucial role for so-called non-reductive physicalism because it is supposed to secure both the ontological autonomy of mental properties and, despite their irreducibility, their ability to make a causal difference to the course of the causally closed physical world. For a long time however, the nature of realization has largely been ignored in the philosophy of mind until a couple of years ago authors like Carl Gillett, Derk Pereboom, or Sydney Shoemaker proposed accounts according to which realization is understood against the background of the so-called ‘causal theory of properties’. At least partially, the hope was to solve the problem of mental causation, in particular the kind of causal exclusion reasoning made famous by Jaegwon Kim, in a way acceptable to non-reductive physicalists. The paper asks whether a proper explication of the realization relation can indeed help explain how physically realized mental properties can be causally efficacious in the causally closed physical world and argues for a negative answer: it is important for the non-reductive physicalist to understand what exactly the realization relation amounts to, but it does not solve the problem of mental causation.
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Notes
Walter (2006a, 2008) argues that the supervenience argument fails as an argument against non-reductive physicalism. The problem is that its central premise—the principle of causal exclusion according to which “[n]o single event can have more than one sufficient cause at any given time—unless it is a genuine case of causal overdetermination” (Kim 2005, p. 42)—can be defended only by presupposing a ‘production conception of causation’ (i.e., causation as transfer of momentum, energy or some other physical quantity) which is both implausible and rejected by the non-reductive physicalist.
Compare Putnam (1967, p. 436): “the functional-state hypothesis is not incompatible with dualism!”.
To distinguish it from the also asymmetric causal relation, the realization relation is taken to be synchronic, not diachronic.
The context contains more than just time. Claiming that pain is realized in humans by c-fiber firing does not commit one to claiming that artificially stimulated c-fibers in a laboratory lead to pain experiences. It is only in the right context, i.e., given an appropriate structural embedding in a complex system (typically specified by a property’s functional role; see below) that the dependence expressed by the realization idiom holds. Shoemaker (1981) thus distinguishes between core realizers and total realizers: a core realizer is a physical property which together with other structural properties realizes a mental property (c-fiber firings could thus be a core realizer of pain), while the total realizer is a combination of the core realizer and these structural properties. When the realization relation is characterized as a dependence relation between a property and its realizer, ‘realizer’ must thus always be read as ‘total realizer’. In the text this fact is captured by the talk about contexts. For a more detailed discussion of the context-dependence of realization see Wilson (2001).
‘Functionalism’ here means role functionalism, not filler functionalism. It is only in the context of role functionalism that talk about realization as a non-reductive relationship makes sense, since for filler functionalism the realization relation collapses into (species specific) property identities.
Realizationfunc has recently regained supporters. Polger argues that “[p]roperty/state instance P realizes property/state instance G iff P has the function F G (x)” (Polger 2007, p. 251) and Larry Shapiro maintains that “[t]o say that a kind is multiply realizable is to say that there are different ways to bring about the function that defines the kind” (Shapiro 2000, p. 644; see also Shapiro 2004, p. 67). However, neither of them is interested in mental causation.
The importance of an explanatory element was also stressed by Horgan: “the sort of inter-level relation needed by the materialist … is not bare supervenience, but rather what I hereby dub superdupervenience: viz., … supervenience that is robustly explainable in a materialistically explainable way …” (Horgan 1993, p. 566) and Kim: “to have a physical realization is to be physically grounded and explainable in terms of the processes at an underlying level” Kim (1992b, p. 328).
Influential answers include the appeal to explanatory considerations (Baker 1993; Jackson and Pettit 1990a, b), counterfactual connections (Lepore and Loewer 1987, 1989), or non-strict mentalistic laws (Fodor 1989; McLaughlin 1989), and Stephen Yablo’s suggestion that mental properties are determinables of their physical realizers. Baker’s approach is criticized in Walter (2007a), Jackson and Pettit’s in Walter (2005), and Yablo’s in Walter (2007b).
RealizationS/C nicely illustrates a point made above (see pp. 234−246): the explanatory connection between P and F is not stipulated by definition, but a result of the nature of the realization relation. That the causal powers individuative of F are a subset of the causal powers individuative of P explains why the instantiation of P by an object in a context explains the instantiation of F by that object in that context.
Compare Pereboom (2002, p. 500): “But neither will a … token-identity thesis for these causal powers hold. For if it did, then the causal powers to which the psychological explanation refers would in the last analysis, in fact, be microphysical”.
Like Realization S/C Realization P entails an explanatory connection: “on this view there will be a significant degree to which causal powers of higher-level tokens could be explained in terms of the causal powers of their microphysical constituents” (Pereboom 2002, p. 504).
For instance, Gillett (2003) argues, the hardness of a diamond is realized by the (instantiations of the) properties of the atoms that constitute the diamond.
He refers to Pereboom and Kornblith (1991, p. 131) who argued that “[t]he causal powers of a token of kind F are constituted of the causal powers of a token of kind G just in case the token of kind F has the causal powers it does in virtue of its being constituted of a token of kind G.” However, the ‘in virtue of’ locution invoked here to elucidate the relation of constitution between causal powers is arguably as unclear as the constitution idiom itself.
See also Pereboom and Kornblith (1991, pp. 143, 144):
[M]ental causal powers are wholly constituted of physical causal powers; they are neither identical to (nor are they necessary and sufficient for) them, nor wholly independent of them. The psychological explanation of an event does not compete with its physical counterpart because the mental causal powers referred to in the psychological explanation are wholly made up of the physical causal powers referred to in the physical explanation.
Otherwise, the result would be an unacceptable inflation of properties: in addition to having a maximum speed of 130 mph, the car would then also have the property of having a maximum speed of <140 mph, the property of having a maximum speed of <150 mph, the property of having a maximum speed of >120 mph and so on ad infinitum.
Clapp is very clear about this:
[T]he definition [of realization stated above on pp. 391–394; S.W.] helps to clarify that NRP [non-reductive physicalism; S.W.] is incompatible with the metaphorical claim … that mental properties exist ‘over and above’ their realizors. According to the above well-motivated definition, multiply realized mental properties, though real and causally efficacious, are better thought of as parts of their physical realizors. (Clapp 2001, pp. 132–133; see also Heil 1999, p. 194)
The problem is most obvious in the case of Realization S/C: if one insists that a realizer property and the property it realizes contribute to the same causal powers of their bearers, we are, so to speak, double-counting causal powers. This is a major flaw in the metaphor of causal inheritance: if Paul inherits thousand bucks from his uncle, it is not that now each of them has thousand bucks, and likewise for causal powers.
It seems that in the case of Realization S/C realized properties cannot even be said to contribute to the causal powers of their bearers at all. The instantiation of a property P by an object o in context u contributes to o’s having causal powers c iff (1) the fact that o in u instantiates properties P, P′1,…,P′ n is minimally sufficient for o’s having c in u, and (2) the fact that o in u instantiates P is necessary for o’s having c in u. Yet, the instantiation of a realizedS/C property is not necessary for its bearer’s having the causal powers it has because had it only had the realizer properties, it would have had the same causal powers.
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Walter, S. Taking realization seriously: no cure for epiphobia. Philos Stud 151, 207–226 (2010). https://doi.org/10.1007/s11098-009-9425-3
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DOI: https://doi.org/10.1007/s11098-009-9425-3