1
Anomalous monism is motivated by three principles:
- The Principle of Causal Interaction: “at least some mental events interact causally with physical events”[1].
- The Principle of the Nomological Character of Causality: “where there is causality there must be law”[2].
- The Principle of the Anomalism of the Mental: “there are no strict deterministic laws on the basis of which mental events can be predicted and explained”[3].
In addition, Davidson’s position is monist: the physical world is a causally closed system, and thoughts, beliefs, etc. are physical.
The first two of Davidson’s principles are intuitively plausible. Most of our actions in daily life are premised upon the notion that mental events can cause physical events and vice versa. For us to accept that one event caused another we typically require that the second event was necessitated by the first and the existence of a covering law seems to provide one way to understand causal necessity.
The Principle of the Anomalism of the Mental is less intuitive, but is related, for Davidson, to the distinct characters of physical and mental statements: “There are no strict psychophysical laws because of the disparate commitments of the mental and physical schemes”[4]. Mental and physical descriptions are both subject to revision, but the revision of mental descriptions depends on “the constitutive ideal rationality”[5] in a way that the revision of physical descriptions does not. So the “nomological slack between the mental and the physical is essential as long as we conceive of man as a rational animal”[6].
In order to resolve the apparent contradiction between these three principles, Davidson proposes that any particular mental event is token-identical with a physical event. There may be psycho-physical interaction because there may exist a physical description of a mental event that relates it to a distinct physical event in terms of a law. In order to ensure that the third principle is upheld the relationship between the mental and the physical properties associated with an event must not be law-like in nature. Davidson proposes that the relationship between them is that the mental supervenes on the physical: “there cannot be two events alike in all physical respects but differing in some mental respect”[7].
2
Kim’s causal exclusion argument considers a mental event, m, instantiating a mental property, M, where m is the cause of some other mental event, m*, instantiating a mental property, M*. Now, m* has physical properties, P*, which, by the definition of supervenience, necessarily imply the existence of M*. Kim argues[8] that we are committed to a position of downward causation where the occurrence of M is the cause of the occurrence of P*.
The event m has physical properties, P, which imply the existence of M. Therefore, if M is sufficient for the occurrence of P*, “it follows that P is sufficient, as a matter of law, for P*”[9]. But we cannot have two separate sufficient causes for P* and so, if M is not identical with P, mental properties appear to be epiphenomenal.
3
A simple way of expressing Kim’s argument might be to say that if we were to change or remove the mental properties associated with an event, it would make no difference to any causal relationships that include that event. Does this suffice to show that the mental properties are causally irrelevant in anomalous monism?
In the context of Davidson’s philosophy it is events, however described, and not properties that are related by cause and effect. Because mental properties supervene on physical properties you cannot change or remove the mental properties without also changing the physical properties. There is no logically possible world in which the mental properties could be so rearranged whilst the physical properties are preserved. So this does not suffice to show that mental properties are causally irrelevant.
Yet in order for two events to be related by cause and effect, they need fall under a law. And they can only do so because their physical properties play a role in the law in question. So physical properties appear to play a role in the attribution of causality that mental properties do not.
4
Consider a billiard ball striking another and causing it to move. The colour of the billiard ball is causally irrelevant to the movement of the second ball in the sense that whether it is struck by a white or red ball, the second ball will move in the same way. In contrast the mass, velocity and elasticity of the ball are causally relevant because they play roles in the laws of physics that describe the situation.
For anomalous monism, if the mental properties are different then it is not the same event. So the mental properties are a necessary requirement for that event to cause that effect. But this is as true of our example of the billiard balls. If the first ball were red and not white then the striking of the second ball would be a different event.
Because of the relationship of supervenience, if the mental properties are to change, there must be a change in the physical properties. But, in practice, if we were to change the colour of the billiard ball there would also be some small change in the mass or internal constitution of the ball. There is no way to repeat the experiment in such a way as to hold the causally relevant properties strictly constant whilst varying the causally irrelevant ones.
Yet we still accept that the colour is causally irrelevant. So the fact that the mental properties are a necessary requirement for a particular event to cause a particular effect does not seem to suffice to demonstrate that the mental properties are causally relevant.
5
Suppose, in contrast, that mental properties are not such an orthogonal description to physical properties as might be suggested by the broadest notion of supervenience. Only physical properties sharing some, possibly loosely defined, characteristics can be described as instantiating some mental property. Under such circumstances the mental property may have explanatory power without being identifiable with any particular physical property.
Consider the theory of evolution[10]. Every instance of survival, reproduction and variation has a proximate cause which can be described without reference to evolution. Yet evolution is explanatorily successful, partially because, whilst there are many ways for an organism to be fit, all those ways form a family of properties capable of playing a role in a higher level theory. One could choose to describe such a high level property as explanatorily successful and causally irrelevant, but one could also describe it as causally relevant albeit not causally determinative.
Davidson raises the possibility of non-strict or statistical laws linking mental and physical properties[11]. The three principles underlying anomalous monism would still be satisfied since the third principle only forbids “strict deterministic laws”. It is Kim’s position that such a view is still subject to his causal exclusion argument[12], but perhaps all we desire is that mental properties play a valuable explanatory role and hence are not epiphenomenal in any vicious sense.
[1]Davidson, D., ‘Mental Events’, in Essays on Actions and Events, Oxford University Press, Oxford, 2001, p. 208.
[2]ibid.
[3]ibid.
[4]ibid., p. 222.
[5]ibid., p. 223.
[6]ibid.
[7]ibid., p. 214.
[8]Kim, J., ‘The Non-Reductivist’s Troubles with Mental Causation’, in Heil, J., Mele, A. (ed.), Mental Causation, Oxford, 1993, p. 204-206.
[9]ibid., p. 207.
[10]The analogy was suggested by Ian McEwan, although I have, no doubt, extended it beyond the purposes for which it was originally intended.
[11]Davidson, D., ‘Thinking Causes’, in Heil, J., Mele, A., op. cit., p. 3-17.
[12]Kim, J., ‘Can Supervenience and Non-Strict Laws Save Anomalous Monism?’, in Heil, J., Mele, A., op. cit., p. 25-26.
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