Copyright © 1999 Massachusetts Institute of Technology
Supervenience is a determination relation, often thought to hold between physical characteristics and mental characteristics. In philosophy of mind, the concept of supervenience is sometimes employed as a way of articulating the metaphysical thesis of PHYSICALISM. The notion of supervenience, originally employed in ethics, was introduced into philosophy of mind by Donald Davidson (1970, 1973), who formulated the thesis that mental characteristics are supervenient on physical ones: "It is impossible for two events (objects, states) to agree in all their physical characteristics . . . and to differ in their psychological characteristics" (Davidson 1973: 716). This supervenience claim is weaker than certain other claims about physical-mental relations sometimes advocated in philosophy of mind -- for instance, that mental characteristics are identical to, or are definable from, or are lawfully coextensive with, physical characteristics.
One commonly cited reason to favor physical/psychological supervenience over any of these stronger, more reductive, conceptions of the relation between the physical and the mental is that psychological characteristics allegedly are multiply realizable (i.e., multiply implementable) by physical ones. For instance, mental properties might get physically realized very differently in certain actual or possible nonhuman creatures (e.g., Martians) than in humans. Furthermore, for some species of actual or possible creatures (perhaps including humans), a given psychological characteristic might be physically multiply realizable within the species, or even in a single creature.
The physical characteristics that determine a given psychological characteristic M of a given creature (on a particular occasion when M is instantiated) are called the super-venience base for M (on that occasion). Typically the supervenience base will include not only the physical property P that physically realizes M in the creature with characteristic M, but also certain physical-structural characteristics of the creature in virtue of which the property P plays the causal role requisite for being a realization of M. For instance, the supervenience base for the property wanting some ice cream on a given occasion, will include not only the neurochemical property P that physically realizes this desire-property in a given person, but also various persisting structural features of the person's brain and body in virtue of which P plays a suitable desire-implementing causal role (e.g., the role of propelling the person's body toward a location where the person believes ice cream can be obtained).
Supervenience often figures in philosophical discussions of mental causation. It is sometimes suggested (e.g., Kim 1979, 1984) that causal efficacy and explanatory relevance are "transmitted" across levels of description, via supervenience connections, from physical characteristics to mental ones. The idea is that mental characteristics figure in "supervenient causation" -- even though all human behavior, described as bodily motion, in principle is causally explainable in physico-chemical terms (see MENTAL CAUSATION).
A distinction is commonly made between intentional (representational) mental characteristics and qualitative (phenomenal) mental characteristics; and it is sometimes maintained that the former are supervenient on the physical in a way that the latter are not. (Intentional characteristics are the kind typically expressed by mentalistic locutions containing "that"-clauses, e.g., "believes that MIT is in Boston." Qualitative characteristics, or QUALIA, are the distinctive WHAT IT'S LIKE features of sensory experiences like seeing a bright red color patch, or smelling rotten eggs, or stubbing one's toe.) Intentional characteristics are widely thought to be logically, or conceptually, supervenient on physical characteristics (e.g., Chalmers 1996) -- so that there is no "possible world" that is a perfect physical duplicate of the actual world, but differs from the actual world in the distribution of intentional mental properties. By contrast, it is sometimes claimed (e.g., Chalmers 1996) that qualia are not logically supervenient on the physical, because allegedly the following kinds of physical-duplicate worlds are conceptually coherent possibilities: (1) a physical-duplicate world in which color qualia are paired with the relevant neural states in the human visual cortex in ways that are systematically inverted relative to actual-world neural/qualia pairings (an "inverted qualia" world); and (2) a physical-duplicate world in which qualia are absent altogether (an "absent qualia" world).
Even if qualia are not logically supervenient on physical characteristics, they still might exhibit a weaker kind of dependence: nomological (i.e., lawful) supervenience. The nomological supervenience of qualia would mean there are fundamental laws of nature, over and above the basic laws of physics, linking certain physical (or perhaps certain functional) characteristics of certain physical systems (e.g., humans and other sentient creatures) with the concurrent presence of qualia -- a view defended in Chalmers (1996). Arguably, such a position would be a version of naturalism about qualia, but not a version of physicalism. Issues of mental causation would arise for such a view, because it is sometimes maintained (e.g., Horgan 1987) that if qualia supervene on physical characteristics only nomically and not in a stronger way, then qualia are epiphenomenal -- that is, they have no real causal efficacy or explanatory relevance vis-à-vis human behavior.
Supervenience issues also arise with respect to intentional mental characteristics. It is often claimed that for at least some intentional properties, the minimal supervenience base includes more than the intrinsic physical features of the person instantiating the property (at the time of instantiation); it also includes certain relational connections between the person and the wider environment. One very influential source for such claims is the TWIN EARTH thought experiment in Putnam (1975). An Earthling and a Twin Earthling who are just alike in all intrinsic physical respects could differ mentally: the Earthling is having a thought about water (viz., H2O), whereas the Twin Earthling is having a thought about twater (viz., XYZ). The moral, apparently, is that the supervenience base for an intentional mental characteristic like wanting some water involves not merely the current intrinsic physical properties of the person who currently has this mental property, but also certain relational connections between the person and the person's physical -- and/or social, and/or historical, and/or evolutionary -- environment. Such mental properties are said to have wide content, because the supervenience base for such a property extends beyond the current intrinsic physical characteristics of the creature currently instantiating the property; wide-content characteristics, as the saying goes, are not supervenient upon "what's in the head." By contrast, intentional mental characteristics that do supervene upon a creature's current intrinsic physical characteristics are said to have NARROW CONTENT.
A variety of interrelated issues concerning wide and narrow content have received active discussion in recent philosophy, and have direct implications for the foundations of cognitive science. These include the following:
Discussion of such questions has occurred in an intellectual climate where two broad currents of thought have been dominant. One approach assumes that most, or perhaps all, intentional mental states have both wide content and narrow content (e.g., Fodor 1980, 1987, 1991). A second approach eschews narrow content altogether, and construes mental intentionality as essentially a matter of suitable relational connections between intrinsic physical states of a creature and certain features of the creature's current environment and/or its evolutionary/developmental history (e.g., Dretske 1981, 1988; Millikan 1984; Fodor 1994). But some philosophers vigorously challenge both orientations -- for instance, David Lewis (1994), whose dissident remarks are eminently sensible.
Two longer overview discussions of supervenience are Kim (1990) and Horgan (1993). Useful collections include Horgan (1984), Beckermann, Flohr, and Kim (1992), and Kim (1993).
Beckermann, A., H. Flohr, and J. Kim, Eds. (1992). Emergence or Reduction? Essays on the Prospects of Nonreductive Physicalism. Berlin: de Guyter.
Chalmers, D. (1996). The Conscious Mind: In Search of a Fundamental Theory. New York: Oxford University Press.
Davidson, D. (1970). Mental events. In L. Foster and J. W. Swanson, Eds., Experience and Theory. Amherst: University of Massachusetts Press.
Davidson, D. (1973). The material mind. In P. Suppes et al., Eds., Logic, Methodology, and the Philosophy of Science. Amsterdam: North-Holland.
Dretske, F. (1981). Knowledge and the Flow of Information. Cambridge, MA: MIT Press.
Dretske, F. (1988). Explaining Behavior: Reasons in a World of Causes. Cambridge, MA: MIT Press.
Fodor, J. (1980). Methodological solipsism considered as a research strategy in cognitive science. Behavioral and Brain Sciences 3:63-109.
Fodor, J. (1987). Psychosemantics: The Problem of Meaning in the Philosophy of Mind. Cambridge, MA: MIT Press.
Fodor, J. (1991). A Theory of Content and Other Essays. Cambridge, MA: MIT Press.
Fodor, J. (1994). The Elm and the Expert: Mentalese and Its Semantics. Cambridge, MA: MIT Press.
Horgan, T., Ed. (1984). The Concept of Supervenience in Contemporary Philosophy, Spindel Conference Supplement, Southern Journal of Philosophy 22.
Horgan, T. (1987). Supervenient qualia. Philosophical Review 96:491-520.
Horgan, T. (1993). From supervenience to superdupervenience: Meeting the demands of a material world. Mind 102:555-586.
Kim, J. (1979). Causality, identity, and supervenience in the mind-body problem. In P. French, T. Uehling, and H. Wettstein, Eds., Midwest Studies in Philosophy, 4. Minneapolis: University of Minnesota Press.
Kim, J. (1984). Supervenience and supervenient causation. In Horgan (1984).
Kim, J. (1990). Supervenience as a philosophical concept. Metaphilosophy 21:1-27.
Kim, J. (1993). Supervenience and Mind: Selected Philosophical Essays. Cambridge: Cambridge University Press.
Lewis, D. (1994). Reduction of mind. In S. Guttenplan, Ed., A Companion to the Philosophy of Mind. Cambridge, MA: Blackwell.
Millikan, R. (1984). Language, Thought, and Other Biological Categories: New Foundations for Realism. Cambridge, MA: MIT Press.
Moore, G. E. (1922). The conception of intrinsic value. In Philosophical Studies. New York: Harcourt, Brace, and Company.
Putnam, H. (1975). The meaning of "meaning." In K. Gunderson, Ed., Language, Mind, and Knowledge, Minnesota Studies in the Philosophy of Science, 7. Minneapolis: University of Minnesota Press .
Copyright © 1999 Massachusetts Institute of Technology