Abstract
Several philosophers (e.g., Ehring (Nous (Detroit, Mich.) 30:461–480, 1996); Funkhouser (Nous (Detroit, Mich.) 40:548–569, 2006); Walter (Canadian Journal of Philosophy 37:217–244, 2007) have argued that there are metaphysical differences between the determinable-determinate relation and the realization relation between mental and physical properties. Others have challenged this claim (e.g., Wilson (Philosophical Studies, 2009). In this paper, I argue that there are indeed such differences and propose a “mechanistic” account of realization that elucidates why these differences hold. This account of realization incorporates two distinct roles that mechanisms play in the realization of mental (and other special science) properties which are implicit, but undeveloped, in the literature—what I call “constitutive” and “integrative” mechanisms. I then use these two notions of mechanism to clarify some debates about the relations between realization, multiple realizability, and irreducibility.
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Notes
Jessica Wilson (2009) has recently defended the claim that mental–physical realization has the “core” feature of the determinable–determinable relation (the “specificity principle” expressed by the quotation from Yablo above) and all of the features that “flow” from this feature and are required to solve the problem of mental causation. She proposes a “proper subset” account of determination, which is very similar to the subset account of realization (e.g., Shoemaker 2007). As will become clear below, I am happy to allow that there is a general relation of realization or “determination” that applies to both the mental/physical case and “traditional” determinable-determinate cases and even perhaps that this relation provides a basis for solving the problem of mental causation. Thus, my motivation for distinguishing the mental–physical realization from a more restrictive determination relation differs from the motivations of Ehring, Funkhouser, and Walter. I am more concerned with the relations between properties at different levels of abstraction (i.e., those that play a role in different sciences) and what is required of a relation that establishes that mental properties are physicalistically acceptable.
As I discuss below, this is related to the fact that a determinate falls under only a single hierarchy of determinables. This point is also related to what Ehring calls the “difference principle: distinct same-level determinates of a determinable Q differ with respect to Q (are different Q’s)” (1996, p. 471).
I am officially neutral on whether the aspects that characterize realizers include those that characterize the properties they realize in addition to others, or whether the aspect spaces for realized properties and their realizers are disjoint (although I incline toward the former view). The answer to this question will be relevant at one point in Sect. 5. Wilson (2009) argues, in effect, that psychological determinables may have explicitly physical aspects. This may be true, but I suspect that such physical aspects cannot be essential to psychological properties. If they were, then such psychological properties would be essentially physical, and physicalism, if true at all, would be necessarily true.
I use the terms ‘high-level’ and ‘special science’ interchangeably.
As Richard Boyd pointed out (personal communication), these claims will hold only for non-conjunctive properties, since the property of being a red square will of course determine both being red and being square. Further, he raised the example of “cross-modal” adjectives like warm and grating, which might be used to compare colors and tones, and thus might be thought of as determinables covering both colors and tones. One way to handle such cases is to note that such adjectives are properties of properties and restrict the requirements on determinables and determinates to properties of individuals.
One might think that determinate sounds or tones are not incompatible in this way. However, while two sounds may be present in the same room at the same time, their waveforms will occupy different regions of that room at any given instant (or will interfere to produce a third tone). Thanks to Mark Crimmins for raising this point.
Wilson (2009) claims that different sciences may treat the same determinable as being characterized by different aspects (i.e., that the aspects that characterize a particular property may be science-relative). Even if this is true, the claim made in the text still holds as long as we hold fixed the relevant science. (See the end of note 1.) Further, I am skeptical about Wilson’s claim that her “proper subset” causal power account of determination can accommodate the science-relativity of aspects. This point should be reflected in different sciences assigning different numbers of dimensions to the aspect space for mental properties. As Wilson correctly notes: “what looks like a point relative to a particular property space, defined by a specific set of determination dimensions, is (under the effective “magnification” associated with a finer level of metaphysical grain) in fact an extended space, with further (possibly physical) determination dimensions.” However, when she discusses how the “proper subset” account of determination allegedly handles this phenomenon she makes a different point: “The laws of one science may be sensitive to relatively small supersets of the set of causal powers had by the determinable, while the laws of another science may be sensitive to relatively large supersets of the determinable set.” This may be true, but it is a point about different sciences’ sensitivity to different determinates within a common aspect space, not about the structure of the aspect space itself being science-relative.
This claim is a special case of Ehring’s (1996, p. 470)“principle of exclusion: If P 1 , …, P n is a complete set of same-level determinates of Q, then if x has Q, then x has only one of the properties in this set”. Walter (2007, p. 226) argues that the principle of exclusion is not a necessary condition on the determinable/determinate relation. He cites cases of vague, same-level determinates such as being red and being orange and suggests that objects which have a property that is a borderline case between such same-level determinates violate the principle of exclusion. Even if Walter is correct that such cases are counterexamples to the general principle of exclusion, they pose no problem for incompatibility as formulated above, assuming that maximally determinate properties have no borderline cases.
Note that this is a total realizer—a realizer whose instantiation is metaphysically sufficient for (i.e., necessitates) the instantiation of having an acute pain—not a core realizer (such as having Aδ-fibers firing), whose instantiation does not necessitate the instantiation of the realized property. If the laws of nature are metaphysically contingent, then they should be also included in the total realizer.
Several authors have discussed relations that are similar to multiple determinativity, e.g., Menzies (1988), Gasper’s “multiple supervenience” (1992), and Endicott’s “constructival plasticity” (1994). Menzies discusses many interesting examples where two properties supervene on the same base property; multiple determinativity is most like the examples he discusses under “typical causal role supervenience” (except it is explicitly about total realizers). Philip Gasper (1992) discusses a similar phenomenon, which he calls “multiple supervenience,” and argues that it blocks reductive explanation. But Gasper cites an example of what Menzies calls “logical supervenience” where a hierarchy of determinables (being less than 1 cm in length, being less than 0.9 cm in length, etc.) supervenes on a single molecular base (1992, p. 668) as an example of multiple supervenience. Determinates of a given determinable obviously exhibit this phenomenon, but I claim that these determinates are not multiply determinative (in the right way)—they do not realize different kinds of properties, properties which fall under different ultimate determinables. Menzies’ and Gasper’s discussions are too broad—conflating relations that should be kept distinct. Endicott’s “constructival plasticity” is simply the phenomenon of a single core realizer realizing incompatible properties when embedded in different total realizers. By contrast, multiple determinativitiy is not the converse of multiple realizability. It is not the claim that a (core) physical realizer could have realized different mental properties from those it actually does.
The integrative role of mechanisms is similar to what Craver (2007), following Wesley Salmon, calls the “etiological” aspect of causal-mechanical explanation. However, the integrative role of mechanisms is both backward- and forward-looking.
Note that I am not I imposing the restriction that the integrative network be causal; it may be a set of lawlike relations between properties that are mathematically, intentionally, or otherwise individuated (see Polger 2007, pp. 239–247 for discussion of such cases). For the purposes of this paper, I remain neutral on the question of whether such non-causal cases are relevant to the realization of mental properties. In general, I will restrict my discussion to causal cases for simplicity.
Block (1997) seems to have something like an integrative mechanism in mind when he writes: “The relations among temperature, pressure, entropy, etc., are mirrored by relations among mean molecular kinetic energy, momentum exchange, etc., and the latter family provide[s] a mechanism for explaining the relations among the former. That is what makes the latter properties realize the former, or anyway it is closely connected to what makes for this realization” (118, italics added).
Conductance (like resistance and current) is a macroscopic property of a sample of a substance as a whole, as opposed to conductivity (like resistivity and current density), which is a microscopic property, having values at every point in a body.
Arguably, different types of integrative mechanism will correspond to different special science domains. e.g., there will be biological, psychological, and geological integrative mechanisms. For some explanatory purposes, one might want to distinguish sub-types of integrative mechanism as well (e.g., affective and cognitive mechanisms in psychology). Wilson (2009) suggests that a special science property can even have low-level physical aspects; this will be true if, e.g., relations to low-level physical properties are included in some integrative mechanism for the special science property.
I include the parenthetical clause to allow for the possibility of realized properties that are not causally individuated (see Polger 2007, pp. 239–247). In such cases, condition (a) will be vacuously satisfied.
An anonymous referee raised the concern that the notion of a mechanism presupposes, rather than explains, the realization relation. While this worry merits further discussion, I should note that I am not committed to a reductive analysis of realization in terms of a conceptually prior notion of mechanism.
I suspect that Carl Craver’s discussion of “constitutive relevance”—how to determine whether a part of a system S is a component in the mechanism for S’s having or exercising a certain capacity (2007, pp. 139–160)—could be adapted to help determine whether the differences between components of constitutive mechanisms count as cases of substantive multiple realizability. For example, if one took an aluminum lever-style corkscrew and gradually replaced its aluminum atoms with iron, carbon, and chromium atoms (that bear the appropriate relations to one another) and the resulting corkscrews performed in ways that were expected given the equations or functional relationships corresponding to the relevant integrative mechanism, then this would support the claim that this is a case of substantive multiple realizability, since the changes in composition would be relevant to the differences in the corkscrews’ functionality as corkscrews. See the discussion below.
Part of the difficulty of evaluating this case is the artificiality involved in talking about “corkscrew science” or a “corkscrew level of abstraction.” It is very plausible that a “science of corkscrews” is merely part of the study of simple machines (or of the mechanics of rigid bodies, more generally). This would suggest that the latter characterization of the relevant aspect space is to be preferred.
This assumes, I think, that the aspects that characterize the realized property are a proper subset of those that characterize its realizer. If one denied this, and claimed that the respective aspect spaces were disjoint (see note 3), then there would be no property identity, but the general point I am making about the multiple realization of determinable properties would still hold: sometimes distinct realizers of determinable property X may be put in a one-one correspondence with determinates that differ in their X-ness.
Of course, this still could count as substantive multiple realization of a single “maximally determinate” kind of corkscrew. But, it is unlikely that any interesting “corkscrew science” would individuate kinds of corkscrews this coarsely. See note 19.
On the subset model of realization, we have one causal profile corresponding to P, which has two distinct but overlapping subsets corresponding to being an airfoil and being a thermoregulator, respectively.
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Acknowledgments
A previous version of this paper was presented at the 2008 Philosophy of Science Association Meeting in Pittsburgh, PA. Thanks to the members of that audience, especially Thomas Polger and Lawrence Shapiro, for their comments and questions. I am also grateful to Richard Boyd, Anne Nester, and Sydney Shoemaker for helpful conversations and correspondence. Some of the material in this paper is based upon work that was supported under a National Science Foundation Graduate Research Fellowship. Additional financial support was provided by a Faculty Summer Research Grant from the College of William & Mary.
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Haug, M.C. Realization, determination, and mechanisms. Philos Stud 150, 313–330 (2010). https://doi.org/10.1007/s11098-009-9409-3
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DOI: https://doi.org/10.1007/s11098-009-9409-3