Copyright © 1999 Massachusetts Institute of Technology
The traditional doctrine of epiphenomenalism is that mental phenomena are caused by physical phenomena but do not themselves cause anything. Thus, according to this doctrine, mental states and events are causally inert, causally impotent; they figure in the web of causal relations only as effects, never as causes. James Ward (1903) coined the term epiphenomenalism for this doctrine. However, William JAMES (1890) was the first to use the term epiphenomena to mean phenomena that lack causal efficacy. (It is possible that his use of the term was inspired by the medical use of epiphenomena to mean symptoms of an underlying condition.) Huxley (1874) and Hodgson (1870) earlier discussed the doctrine of epiphenomenalism under the heading of "Conscious Automatism." They both held that conscious states are caused by physiological states but have no causal effect on physiological states (see Caston 1997).
According to proponents of epiphenomenalism, mental phenomena seem to be causes only because they figure in regularities. For example, instances of a certain type of mental occurrence M (e.g., trying to raise one's arm) might tend to be followed by instances of a type of physical occurrence P (e.g., one's arm's rising). But it would be fallacious to infer from that regularity that instances of M tend to cause instances of P: it would be to commit the fallacy of post hoc, ergo propter hoc. According to the epiphenomenalist, when an M-type occurrence is followed by a P-type occurrence, the occurrences are dual effects of some common physical cause.
Epiphenomenalism is a shocking doctrine. If it is true, then a PAIN could never cause us to wince or flinch, something's looking red to us could never cause us to think it is red, and a nagging headache could never cause us to be in a bad mood. Indeed, if epiphenomenalism is true, then although one thought may follow another, one thought never results in another. If thinking is a causal process, it follows that we never engage in the activity of thinking.
A central premise in the argument for epiphenomenalism is that for every (caused) event, e, there is a causal chain of physical events leading to e such that each link in the chain determines (or, if strict determinism is false, determines the objective probability of) its successor. Such physical causal chains are said to leave "no gap" to be filled by mental occurrences, and it is thus claimed that mental occurrences are epiphenomena (McLaughlin 1994).
One critical response to this no-gap line of argument for epiphenomenalism is that physical events underlie mental events in such a way that mental events are causally efficacious by means of the causal efficacy of their underlying physical events. The task for proponents of this response is to say what it is, exactly, for a physical event to underlie a mental event, and to explain how mental events can count as causes in virtue of the causal efficacy of their underlying physical events. The underlying relationship is typically spelled out in terms of some relationship between mental and physical event types. An explication of the relationship should yield an account of how causal efficacy can transmit from underlying physical events to mental events. (See the discussion of realization that follows.)
Perhaps the leading response to the no-gap line of argument, however, is that every token mental event is identical with some token physical event or other. According to this token physicalism, an event can be both an instance of a mental type (e.g., belief) and an instance of a distinct physical type (e.g., a neurophysiological type). CAUSATION is an extensional relation between states and events: if two states or events are causally related, they are so related however we may type or describe them. Given that the causal relation is extensional, because particular mental states and events are physical states and events with causal effects, mental states and events are causes, and thus epiphenomenalism is false (Davidson 1970, 1993).
The token-identity response to epiphenomenalism does not, however, escape the issue of how mental and physical types (or properties) are related (McLaughlin 1989; 1993). For it prompts a concern about the relevance of mental properties or types to causal relations. C. D. Broad (1925) characterized the view that mental events are epiphenomena as the view "that mental events either (a) do not function at all as causal-factors; or that (b) if they do, they do so in virtue of their physiological characteristics and not in virtue of their mental characteristics" (1925: 473).
Following Broad, we can distinguish two kinds of epiphenomenalism (McLaughlin 1989):
(Property epiphenomenalism is the thesis that no event can cause anything in virtue of having or being an exemplification of a mental property.) Token epiphenomenalism implies type epiphenomenalism; for if an event can cause something in virtue of falling under a mental type, then an event could be both a mental event and a cause, and thus token epiphenomenalism would be false. However, type epiphenomenalism is compatible with the denial of token epiphenomenalism: mental events may be causes, but only in virtue of falling under physical types, and not in virtue of falling under mental types. Whether type epiphenomenalism is true, and whether certain doctrines about the mind (such as Davidson's (1970) doctrine of ANOMALOUS MONISM, which implies token physicalism) imply type epiphenomenalism, have been subjects of intense debate in recent years (see the essays in Heil and Mele 1993). But one can find the concern about type or property epiphenomenalism even in ancient philosophical texts. Aristotle appears to have criticized the harmonia theory of the soul -- the theory according to which the soul is like the harmonia of a musical instrument, its tuning or mode -- on the grounds that it implies property epiphenomenalism (see Caston 1997).
Type epiphenomenalism is itself a stunning doctrine. If type epiphenomenalism is true, then nothing has any causal powers in virtue of (because of) being an instance of a mental type (or having a mental property). Thus, it could never be the case that it is in virtue of being an urge to scratch that a state results in scratching behavior; and it could never be the case that it is in virtue of a state's being a belief that danger is near that it results in fleeing behavior. If type epiphenomenalism is true, the mental qua mental, so to speak, is causally inert: mental types and properties make no difference to causal transactions between states and events (Sosa 1984; Horgan 1989).
How can mental types be related to physical types so that type epiphenomenalism fails? How can mental types be related to physical types so that an event can be a cause in virtue of falling under a mental type? How must mental types relate to physical types so as not to compete for causal relevance?
The notion of multiple realization is often invoked in response to such questions. It is claimed that mental types are multiply realized by physical types and that sometimes a mental type is causally relevant to a certain effect type, whereas the relevant underlying, realizing physical type is merely a matter of implementational detail (Putnam 1975a; Yablo 1992a, 1992b). This happens whenever instances of the mental type would produce an effect of the sort in question however the mental type is in fact physically realized.
This, of course, raises the issue of what realization is. On one notion of realization, the realization relation is that of determinable to determinate (Yablo 1992a, 1992b). But it is highly controversial whether mental types are determinables of physical types. On a related notion of realization, realization is spelled out in terms of the notion of a causal role and the notion of a role-player. Mental state types are types of functional states: they are second-order states, states of being in a state that plays a certain casual role (Loar 1981). The first-order states that realize them are physical states that play the causal roles in question. The second-order state may be multiply realizable in that there are many different first-order states that play the causal role. It is controversial whether appeal to this notion of realization can warrant the rejection of type epiphenomenalism. For it is arguable that second-order state types are themselves epiphenomena. It is arguably not in virtue of falling under such a second-order state type that a state has causal effects, but rather in virtue of falling under some (relevant) first-order state type (Block 1990).
Another notion of realization treats mental concepts (i.e., concepts of mental states) as equivalent to functional concepts, but treats mental states themselves as first-order states that play the relevant causal role (Armstrong 1968; Lewis 1980). On this view, the concept of mental state M of an organism (or system) is equivalent to the concept of being a state of the organism (or system) that plays a certain causal role R. It is claimed that the states that answer to the functional concepts in question are invariably physical states, but which physical states they are may vary from species to species, or even within a species, perhaps even within a given individual at different times.
Concerns about type epiphenomenalism remain, however. We type intentional mental states not only by their intentional mode (e.g., belief, desire, intention), but also by their content (by what is believed, what is desired, or what is intended). According to externalist theories of content, the content of a mental state can fail to supervene on intrinsic physical states of its occupant (Putnam 1975b; Burge 1979). Two intrinsic physical duplicates could have mental states (e.g., beliefs) with different contents. Thus intentional state types seem to involve contextual, environmental factors. The concern is that the contextual, environmental component of content is causally irrelevant to behavior. This is a problem in that the contents of beliefs and desires figure essentially in belief-desire explanations of behavior. The problem is exacerbated by the fact that on some externalist theories, content depends on historical context (Dretske 1988), and that on some it can depend on social context (Burge 1979).
A concern also remains about whether qualitative mental states (states that have a subjective experiential aspect) are epiphenomena. Our concepts of sensory states -- e.g., aches, pains, itches, and the like -- are arguably not functional concepts in either sense of functional concepts (Hill 1991). This has led some philosophers to embrace token dualism for such states and to maintain both type and token epiphenomenalism for them (Jackson 1982; Chalmers 1996). In rejection of epiphenomenalism for qualitative states, some philosophers argue that sensory concepts are equivalent to functional concepts (White 1991). And some argue that although sensory concepts are not equivalent to functional concepts or physical concepts, nonetheless, sensory properties are identical with neural properties (Hill 1991). Whether PHYSICALISM is true for sensory states raises the mind-body problem in perhaps its toughest form. That a nagging headache can cause one to be in a bad mood and that an itch can cause one to scratch seem to be as intuitive cases of mental causation as one can find. But how, and indeed even whether, a qualitative aspect of a mental state (e.g., the achiness of the headache) can be causally relevant remains an issue of intense debate .
Armstrong, D. M. (1968). A Materialist Theory of Mind. London: Routledge and Kegan Paul.
Block, N. (1990). Can the mind change the world? In G. Boolos, Ed., Meaning and Method: Essays in Honor of Hilary Putnam. Cambridge: Cambridge University Press.
Broad, C. D. (1925). The Mind and Its Place in Nature. London: Routledge and Kegan Paul.
Burge, T. (1979). Individualism and the mental. Midwest Studies in Philosophy 4:73-121.
Caston, V. (1997). Epiphenomenalisms, ancient and modern. Philosophical Review 106.
Chalmers, D. (1996). The Conscious Mind: In Search of a Theory of Conscious Experience. 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. (1993). Thinking causes. In J. Heil and A. Mele, Eds., Mental Causation. Oxford: Oxford University Press.
Dretske, F. (1988). Explaining Behavior: Reasons in a World of Causes. Cambridge, MA: MIT Press/Bradford Books.
Heil, J., and A. Mele, Eds. (1993). Mental Causation. Oxford: Oxford University Press.
Hill, C. (1991). Sensations: A Defense of Type Materialism. Cambridge: Cambridge University Press.
Hodgson, S. H. (1870). The Theory of Practice: An Ethical Enquiry. 2 vols. London: Longmans, Green, Reader, and Dyer.
Horgan, T. (1989). Mental quasation. Philosophical Perspectives 3:47-76.
Huxley, T. H. (1874/1901). On the hypothesis that animals are automata, and its history. Reprinted in T. H. Huxley, Method and Results. Collected Essays, vol. 1. New York: D. Appleton and Company.
Jackson, F. (1982). Epiphenomenal qualia. Philosophical Quarterly 32:127-136.
Lepore, E., and B. Loewer. (1987). Mind matters. Journal of Philosophy 84:630-642.
Lewis, D. (1980). Mad pain and martian pain. In N. Block, Ed., Readings in the Philosophy of Psychology, vol. 1. Cambridge, MA: Harvard University Press.
Loar, B. (1981). Mind and Meaning. Cambridge: Cambridge University Press.
McLaughlin, B. P. (1989). Type dualism, type epiphenomenalism, and the causal priority of the physical. Philosophical Perspectives 3:109-135.
McLaughlin, B. P. (1993). On Davidson's response to the charge of epiphenomenalism. In Heil, J., and A. Mele, Eds., Mental Causation. Oxford: Oxford University Press, 27-40.
McLaughlin, B. P. (1994). Epiphenomenalism. In S. Guttenplan, Ed., A Companion to the Philosophy of Mind. Oxford: Blackwell, pp. 277-288
McLaughlin, B. P. (1995). Mental causation. In Encyclopedia of Philosophy, Supplementary Volume. London: Routledge and Kegan Paul.
Putnam, H. (1975a). Philosophy and our mental life. In H. Putnam, Ed., Philosophical Papers, vol. 2. Cambridge: Cambridge University Press.
Putnam, H. (1975b). The meaning of "meaning." In H. Putnam, Ed., Philosophical Papers, vol. 2. Cambridge: Cambridge University Press.
Sosa, E. (1984). Mind-body interaction and supervenient causation. Midwest Studies in Philosophy 9:271-281.
Ward, J. (1896-98/1903). The Conscious Automaton Theory. Lecture XII of Naturalism or Agnosticism, vol. 2. London: Adam and Charles Black, pp. 34 - 64.
White, S. L. (1991). The Unity of the Self. Cambridge, MA: MIT/Bradford Books.
Yablo, S. (1992a). Mental causation. Philosophical Review 101:245-280.
Yablo, S. (1992b). Cause and essence. Synthese 93:403-499.
Fodor, J. A. (1987). Psychosemantics. Cambridge, MA: MIT Press.
Jackson, F., and P. Pettit. (1988). Broad contents and functionalism. Mind 47:381-400.
Kim, J. (1984). Epiphenomenal and supervenient causation. Midwest Studies in Philosophy 9:257-270.
Kim, J. (1993). Supervenience and Mind. Cambridge: Cambridge University Press .
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