Originated by Donald Davidson, "anomalous monism" is a nonreductive, token physicalist position on the relation between the mental and the physical. According to it, each mental event is a physical event, although mental descriptions are neither reducible to nor nomologically correlated with physical ones. In terms that are ontologically more robust than those used by Davidson, the position asserts identities between individual mental and physical events while denying that mental types or properties are either identical with, or nomologically connected with, physical ones. The position specifically concerns intentional mental phenomena such as beliefs and desires, although it is arguable that it can be extended to cover other mental phenomena such as sensations.
Davidson's argument for this position results from an attempt to reconcile three apparently inconsistent principles, two of which he finds independently plausible and the third of which he defends at length. The first is the principle of causal interaction (PCI), which states that mental events cause physical events and vice versa, causality being understood as relating events in extension. The second is the principle of the nomological character of causality (PNCC), which states that events that are causally related have descriptions under which they instantiate strict causal laws. The third is the principle of the anomalism of the mental (PAM), which states that there are no strict laws in which mental terms figure. The principles appear to conflict in that the first two imply what the third seems to deny—namely that there are strict laws governing causal interactions between mental and physical events.
Davidson argues that the principles can be reconciled by adopting the thesis that each mental event has a physical description and so is a physical event. He further suggests that a sound argument can be constructed from these principles to this thesis. Suppose a mental event, m, causes a physical event, p. Then, by the PNCC, m and p have descriptions under which they instantiate a strict causal law. By PAM this cannot be mental in that it cannot contain mental terminology. Therefore m must have a physical description under which it instantiates a strict causal law, which is to say that it is a physical event. Although the argument is formulated in terms of events and their descriptions, it can be formulated equally effectively in the terminology of events and their properties.
Davidson does not take PAM to be obvious. His defense of it involves the idea that laws bring together terms from the same or similar conceptual domains. Using this idea he argues that the constraints that govern the application of mental terms and their associated concepts to things are normative in nature, involving "constitutive" principles of rational coherence, deductive and inductive consistency, and the like. These principles constitute the distinctive rationalistic normativity that is the earmark of the intentional domain; and Davidson argues that they have no place in physical theory.
The argument for anomalous monism appears to work because of the extensionality of the causal relation and the intensionality of nomologicality. Events are causally related no matter how described; but they are governed by laws only as they are described one way rather than another. This opens up a conceptual space between causality and nomologicality that makes it possible to hold both that mental events that interact causally with physical ones are governed by laws and that there are no strict psychological or psychophysical laws.
Davidson's argument has had a profound effect on discussions of mental causation and token physicalism. Many have found either the PNCC or the PAM questionable and have taken issue with it. However, the main objection to the argument is that, on a certain conception of the relation between causality and laws, it leads either to inconsistency or to epiphenomenalism. According to this conception, laws link events causally by linking certain, but not all, of their descriptions or properties, the causally relevant ones. The question now arises, In virtue of which of their properties do mental events interact causally with physical ones? If the answer is the mental ones, then anomalous monism is threatened with inconsistency since this implies that there are laws in which mental descriptions/properties figure. If the answer is the physical ones, then anomalous monism is threatened with epiphenomenalism since it is in virtue of their physical properties that mental events are causally efficacious. Since PAM is a crucial premise in the argument for anomalous monism, it is the epiphenomenalism charge that poses the real threat to the position.
There is a general question of whether nonreductive token physicalist theories count as proper forms of physicalism since they recognize the existence of irreducibly mental properties. Davidson himself favors supplementing his position with some sort of supervenience thesis, according to which, necessarily, if things (events) are the same with regard to their physical descriptions/properties, then they are the same with regard to their mental descriptions/properties. The principal difficulty in formulating such a thesis is in specifying a dependency relation strong enough to ensure that physical properties determine mental ones without leading to reducibility and hence to type physicalism.
Davidson, D. "Mental Events." In Experience and Theory, edited by L. Foster and J. W. Swanson. Amherst: University of Massachusetts Press, Reprinted in D. Davidson, Essays on Actions and Events (Oxford: Clarendon Press, 1980). The classic statement of the argument for anomalous monism.
Davidson, D. "Psychology as Philosophy." In Philosophy of Psychology, edited by S. C. Brown. London: Macmillan, 1974. Reprinted in D. Davidson, Essays on Actions and Events (Oxford: Clarendon Press, 1980). Discusses anomalous monism and the argument against psychophysical laws.
Davidson, D. "Thinking Causes." In Mental Causation, edited by J. Heil and A. Mele. Oxford: Clarendon Press, 1993. Responds to the charge that anomalous monism leads to the causal inefficacy of the mental.
Honderich, T. "The Argument for Anomalous Monism." Analysis 42 (1982). Classic statement of the inconsistency-or-epiphenomenalism objection to anomalous monism.
Kim, J. "The Myth of Nonreductive Materialism." Proceedings of the American Philosophical Association 63 (1989): 31–47. Argues that nonreductive materialism leads to epiphenomenalism.
Kim, J. "Psychophysical Laws." In Actions and Events: Perspectives on the Philosophy of Donald Davidson, edited by E. LePore and B. McLaughlin. Oxford: Blackwell, 1985. Discusses and defends an interpretation of Davidson's argument against psychophysical laws.
LePore, E., and B. Loewer. "Mind Matters." Journal of Philosophy 84 (1987): 630–641. Discusses the causal efficacy of the mental within the context of physicalism.
LePore, E., and B. McLaughlin, eds. Actions and Events: Perspectives on the Philosophy of Donald Davidson. Oxford: Blackwell, 1985. Articles on Davidson's argument for anomalous monism.
Macdonald, C. Mind-Body Identity Theories. London: Routledge, 1989. Surveys various type-type and token identity theories, and defends a version of nonreductive monism.
Macdonald, C., and G. Macdonald. "Mental Causes and Explanation of Action." Philosophical Quarterly 36 (1986): 145–158. Reprinted in Mind, Causation, and Action, edited by L. Stevenson, R. Squires, and J. Haldane (Oxford: Blackwell, 1986). Defends anomalous monism against the charge of epiphenomenalism.
McLaughlin, B. "Type Epiphenomenalism, Type Dualism, and the Causal Priority of the Physical." Philosophical Perspectives 3 (1989). Discusses the problem of mental causation for anomalous monism.
Cynthia Macdonald (1996)