Anomalous monism

Anomalous monism is a philosophical thesis about the mind–body relationship. It was first proposed by Donald Davidson in his 1970 paper "Mental Events". The theory is twofold and states that mental events are identical with physical events, and that the mental is anomalous, i.e. under their mental descriptions, causal relations between these mental events are not describable by strict physical laws. Hence, Davidson proposes an identity theory of mind without the reductive bridge laws associated with the type-identity theory. Since the publication of his paper, Davidson refined his thesis and both critics and supporters of anomalous monism have come up with their own characterizations of the thesis, many of which appear to differ from Davidson's.

Considering views about the relation between the mental and the physical as distinguished first by whether or not mental entities are identical with physical entities, and second by whether or not there are strict psychophysical laws, we arrive at a fourfold classification: (1) nomological monism, which says there are strict correlating laws, and that the correlated entities are identical (this is usually called type physicalism); (2) nomological dualism, which holds that there are strict correlating laws, but that the correlated entities are not identical (parallelism, property dualism and pre-established harmony); (3) anomalous dualism, which holds there are no laws correlating the mental and the physical, that the substances are ontologically distinct, but nevertheless there is interaction between them (i.e. Cartesian dualism); and (4) anomalous monism, which allows only one class of entities, but denies the possibility of definitional and nomological reduction. Davidson put forth his theory of anomalous monism as a possible solution to the mind–body problem.

Since in this theory every mental event is some physical event or other, the idea is that someone's thinking at a certain time, for example, that snow is white, is a certain pattern of neural firing in their brain at that time, an event which can be characterized as both a thinking that snow is white (a type of mental event) and a pattern of neural firing (a type of physical event). There is just one event that can be characterized both in mental terms and in physical terms. If mental events are physical events, they can at least in principle be explained and predicted, like all physical events, on the basis of laws of physical science. However, according to anomalous monism, events cannot be so explained or predicted as described in mental terms (such as "thinking", "desiring", etc.), but only as described in physical terms: this is the distinctive feature of the thesis as a brand of physicalism.

Davidson's argument for anomalous monism relies on the following three principles:

The first principle follows from Davidson's view of the ontology of events and the nature of the relationship of mental events (specifically propositional attitudes) with physical actions. Davidson subscribes to an ontology of events where events (as opposed to objects or states of affairs) are the fundamental, irreducible entities of the mental and physical universe. His original position, as expressed in Actions and Events, was that event-individuation must be done on the basis of causal powers. He later abandoned this view in favour of the individuation of events on the basis of spatio-temporal localization, but his principle of causal interaction seems to imply some sort of, at least, implicit commitment to causal individuation. According to this view, all events are caused by and cause other events and this is the chief, defining characteristic of what an event is.

Another relevant aspect of Davidson's ontology of events for anomalous monism is that an event has an indefinite number of properties or aspects. An event such as "the turning on of the light-switch" is not fully described in the words of that particular phrase. Rather, "the turning on of the light-switch" also involves "the illumination of the room", "the alerting of the burglar in the kitchen", etc... Since a physical event, such as the action of turning on the light-switch can be associated with a very large variety of mental events (reasons) which are potentially capable of rationalizing the action a posteriori, how is it possible to choose the real cause of my turning on the light-switch (which event is the causal one)? Davidson says that the causal event, in such a case, is the particular reason that caused the action to occur. It was because I wanted to see better that I turned on the light-switch and not because I wanted to alert the burglar in the kitchen. The latter is just a sort of side effect. So, for Davidson, "reasons are causes" and this explains the causal efficacy of the mental.

The principle of the nomological character of causality (or cause-law principle) requires that events be covered by so-called strict laws. Davidson originally assumed the validity of this principle but, in more recent years, he felt the need to provide a logical justification for it. So what is a strict law?

According to Davidson, whenever a particular event E1 is causally related to a second particular event E2, there must be a law such that (C1 & D1) → D2, where C1 represents a set of preliminary conditions, D1 is a description of E1 that, given C1, is sufficient for the occurrence of an event of the kind D2, which represents the description of E2. The cause-law principle was intended by Davidson to include both laws of temporal succession and bridge laws.