Abstract
A popular response to the Exclusion Argument for physicalism maintains that mental events depend on their physical bases in such a way that the causation of a physical effect by a mental event and its physical base needn’t generate any problematic form of causal overdetermination, even if mental events are numerically distinct from and irreducible to their physical bases. This paper presents and defends a form of dualism that implements this response by using a dispositional essentialist view of properties to argue that the psychophysical laws linking mental events to their physical bases are metaphysically necessary. I show the advantages of such a position over an alternative form of dualism that merely places more “modal weight” on psychophysical laws than on physical laws. The position is then defended against the objection that it is inconsistent with dualism. Lastly, some suggestions are made as to how dualists might clarify the contribution that mental causes make to their physical effects.
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Notes
The primary proponent of the Exclusion Argument is Kim (1989a, b, 1993, 1998). Though originally intended as an argument against non-reductive forms of physicalism, the Exclusion Argument can also be formulated as an argument against dualism and for physicalism in general. The latter formulation of the Argument is the one that will be of interest for us, although it should be noted that many of the advocates of the response discussed below employ that response in defense of non-reductive physicalism, not dualism. One of the aims of this paper will be to show that dualists can make use of this response as well.
Not everyone agrees that the latter sort of overdetermination is indeed unproblematic. Merricks (2001), e.g., takes it to be problematic enough to justify the elimination of mindless composites from our ontology. Sider (2003) responds (although he offers other reasons for adopting a position akin to Merricks’ in Sider 2013).
Sider (2003, pp. 721, 723) identifies two further objections to overdetermination that do not depend on whether or not the overdetermining causes are modally distinct; viz., that “overdetermination is metaphysically incoherent”, and that “we have no reason to believe in overdetermining entities.” He argues convincingly, however, that these further objections are either unfounded or inconclusive. Bernstein (2016) raises another potential objection to overdetermination that does not apply to standard cases wherein the overdetermining causes are modally distinct, but which may apply to certain cases wherein they are not. This objection will be addressed in Sect. 6.
Funkhouser’s (2002, p. 340) category of “incorporating overdetermination” is actually a bit narrower than the class of all instances of overdetermination wherein the overdetermining causes are not modally distinct. For he defines incorporating overdetermining causes as those that “‘work through’ the same mechanism,” yet it seems that numerically distinct causes could “work through” different mechanisms to produce the same effect without being modally distinct.
Funkhouser (2002, pp. 344–346) later suggests that incorporating overdetermination may also require a kind of “Pre-established Harmony among Levels,” but I don’t see why this need be so. First, as Funkhouser (2002, pp. 340–341) himself notes, the co-occurrence of incorporating overdeterminers is not miraculous or coincidental; it follows from the fact that they cannot “come apart” like independent overdeterminers can. And second, the existence of “irreducible patterns at distinct levels” that tend towards the same effects may be explained naturalistically along the lines proposed by Block (1997).
See Mellor (1995), Bennett (2003), and Kallestrup (2006). While some (e.g. Bennett 2003) have taken this to show that the joint effects of mental events and their physical bases are not overdetermined at all, for simplicity’s sake, I’ll subsume such views under the position that the inability of physical bases to occur without the mental events they give rise to makes systematic overdetermination by mental and physical causes unproblematic.
This question will be taken up in Sect. 6.
Some might object to dispositional essentialism on the grounds that it violates Hume’s dictum that there are no necessary connections between distinct existences. As Wilson (2010) shows, though, many of the reasons typically offered in support of Hume’s dictum fail to hold up under scrutiny.
Assuming that mental properties are multiply realizable, these laws might be conceived as many-to-one functions from physical descriptions of world-states to psychological descriptions of world-states. In order to ensure that the mental properties instantiated in a given world-state cannot be identified with, reduced to, or fully explained in terms of the physical properties instantiated in that world-state, the dualist must also insist that these psychophysical laws are distinctly non-physical, in that they are not included in or deducible from the totality of purely physical facts.
Thanks to an anonymous referee for pointing this out. The further question of the actual causal contribution that mental events make to their putative physical effects will again be addressed in Sect. 6.
The premise numbers of Kroedel’s argument have been changed to avoid confusion with those of the Exclusion Argument.
Premise [i] follows from the fact that the closest possible world wherein none of m’s physical bases occur is one wherein a violation of the actual physical laws renders the physical cause of m’s actual physical base insufficient to produce it or any other physical base of m. The “lawful evolution” of the world from this point on will then lead to the absence of m (which cannot “lawfully” occur without one of its physical bases) as well as the absence of b, since neither m nor any of m’s physical bases will be there to produce it (Kroedel 2013, p. 3).
Thanks to an anonymous referee for suggesting this name for the view.
For reasons discussed in the following section, MN dualists may allow for possible worlds wherein b and/or m occurs without any of m’s physical bases. Given, however, the additional departures from actuality needed to replace m’s actual physical base with some other type of event that is not one of m’s other physical bases but is nevertheless sufficient for b and/or m, any such worlds will end up being farther from actuality than worlds wherein the absence of m’s physical bases leads to the absence of b and m. So premises [i] and [iii] will still come out true.
See Dennett (1995).
Thanks to an anonymous referee for pointing this out.
Bernstein (2016, pp. 32–33, 37) often attributes this to the fact that the overdetermining causes in such cases are additive. While it is of course much easier to identify the different contributions that overdetermining causes make to their common effect in cases where the former are additive, there are, I think, other ways in which a cause can contribute to its effect that do not rely on its being additive in the sense of contributing a separable, independent force to the vector sum of forces acting upon the object it affects. The second response to Bernstein discussed below exemplifies this point.
Those, e.g. Kim (2007, p. 236), who view the vindication of our sense of agency as requiring that mental events somehow generate or produce their effects will likely see such an approach as the only viable option.
See Gibb (2010) and White (forthcoming).
This doesn’t imply that it is actually possible for p to occur without m.
Thanks to an anonymous referee for encouraging me to address this view.
Some proponents of the “causal-subset” strategy (e.g. Shoemaker 2001, p. 81; Wilson 2011, pp. 129–30) suggest that in cases where a mental cause m and its physical base p both produce an effect e, and the causal powers that p has in addition to those that it shares with m make no difference to the production of e, m is more “proportional” to e than p is, inasmuch as it has fewer causal powers that play no role in the production of e than does p. The greater proportionality of m to e is then taken to show that m is distinctively, and perhaps even uniquely causally efficacious with respect to e. (Thanks to an anonymous referee for pointing this out.) If this proposal is to provide a satisfactory response to Bernstein’s objection, though, it seems to me that the distinctive causal contribution that m’s greater proportionality enables it to make to e must be additional to that made by p. Otherwise the objection will remain that m contributes nothing to e that p does not already contribute on its own. To allow, however, that m does causally contribute something to e that p does not seems equivalent to saying that m has certain causal powers with respect to e that p lacks, in which case m’s causal powers cannot constitute a subset of p’s. As I see it, the appeal to proportionality thus only yields a satisfying answer to Bernstein’s objection if the greater proportionality of m to e endows m with causal powers that e’s physical causes do not have. (See, however, Wilson 2011, p. 135.)
Many thanks to two anonymous referees for their helpful comments.
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White, B. Metaphysical necessity dualism. Synthese 195, 1779–1798 (2018). https://doi.org/10.1007/s11229-016-1308-5
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DOI: https://doi.org/10.1007/s11229-016-1308-5