Anomalous Monism

Overview and Historical Context

Anomalous monism is a theory in the philosophy of mind formulated by the American philosopher Donald Davidson, most famously in his 1970 essay “Mental Events.” It is best understood as a distinctive form of non-reductive physicalism or token-identity theory: all individual mental events are physical events, yet there are no strict, exceptionless laws connecting mental types (such as “being in pain”) with physical types (such as “C‑fiber firing”).

The term combines “monism”, the metaphysical thesis that there is only one kind of substance or basic stuff (in this case, the physical), with “anomalous”, indicating the absence of strict psychophysical laws governing the mental. Davidson’s aim is to reconcile three widely held claims:

1. Mental events are causally efficacious.
2. The physical world is governed by strict laws.
3. The mental cannot be captured in strict, exceptionless laws.

Earlier identity theorists (e.g., J. J. C. Smart, U. T. Place) tended to posit type-type identity between mental and brain states, often suggesting that mental kinds were reducible to neurophysiological kinds under strict laws. Davidson accepts physicalism at the level of individual events but denies this sort of reduction, insisting that mental descriptions are governed instead by normative and holistic principles of rationality rather than physical law.

Anomalous monism has become a central reference point in contemporary debates about mental causation, supervenience, and the autonomy of the mental, influencing later positions such as supervenience physicalism and various forms of non-reductive physicalism and property dualism.

Davidson’s Three Principles

Davidson’s argument for anomalous monism turns on the claim that three plausible principles, when combined, yield his position:

1. The Principle of Causal Interaction
   This principle holds that at least some mental events cause and are caused by physical events. For example, a person’s belief that it is raining (a mental event) can cause them to open an umbrella (a bodily, hence physical, event). Davidson takes this as an empirical and conceptual starting point, rejecting epiphenomenalist views that deny mental causation.

2. The Principle of the Nomological Character of Causality
   Davidson endorses a broadly Humean or law-governed conception of causation: whenever one event causes another, the events fall under strict laws. These strict laws, however, are always stated in a “physical” vocabulary, that is, using predicates suitable for inclusion in a unified natural science. Thus, for any genuine causal relation, there exists some lawlike regularity connecting the events under certain descriptions.

3. The Principle of the Anomalism of the Mental
   According to this principle, there are no strict laws connecting mental predicates with other mental predicates or with physical predicates. Mental descriptions are governed by principles of rationality, interpretation, and holism rather than exceptionless natural laws. For instance, whether a person’s belief is rational or coherent depends on its role in a wider network of beliefs and desires, not on any fixed set of physical parameters.

From these three principles, Davidson draws two key conclusions:

• Since mental events stand in causal relations, and all causation is covered by strict laws in physical terms, it follows that each mental event must also be a physical event under some description. This yields event monism or token identity: every particular mental event is identical with some particular physical event.

• Yet because there are no strict psychophysical laws connecting mental and physical predicates, mental vocabulary remains “anomalous”: irreducible to, and not lawfully coextensive with, any physical vocabulary. Mental kinds cannot be neatly matched to physical kinds in the way temperature can be matched to mean molecular kinetic energy.

In this way, anomalous monism aims to secure both physicalism (everything is physically realized) and the autonomy of the mental (mental explanation and rational appraisal are not replaced by physics).

Implications and Criticisms

Anomalous monism has wide-ranging implications for how mental properties, explanation, and causation are understood, and it has generated extensive critical discussion.

1. Mental Causation and Explanatory Role
Proponents argue that anomalous monism preserves mental causation: a belief can cause an action because the underlying event is physical and thus law-governed, even though the belief-as-such does not enter any strict law. Mental explanations (e.g., “she left because she believed the building was on fire”) are therefore compatible with, and not rival to, physical explanations.

Critics, however, raise concerns about causal exclusion and epiphenomenalism. Influenced by arguments from Jaegwon Kim and others, they contend that if physical descriptions alone figure in strict causal laws, then mental properties may be causally redundant. On this view, it is the event’s physical properties that do all the causal work, with mental properties merely “along for the ride,” thereby threatening the genuine efficacy of the mental.

2. Supervenience and Non-Reductive Physicalism
Anomalous monism has often been interpreted as a forerunner to supervenience physicalism: mental properties supervene on physical properties (no mental differences without physical differences) yet are not reducible to them. Davidson himself spoke of the dependence of the mental on the physical, though he was cautious about technical supervenience formulations.

Supporters suggest that anomalous monism offers a template for non-reductive physicalism, allowing mental phenomena to depend on, but not be reducible to, the physical. This is attractive to those who want to honor both the success of natural science and the distinctiveness of psychological, normative, and interpretive explanations.

Opponents question whether this combination is stable. Some argue that without psychophysical laws, the supervenience of mental on physical remains unexplained or mysterious; others maintain that once supervenience is made precise, it either collapses into reductionism or reintroduces something like laws after all.

3. Anomalism, Rationality, and Normativity
A central feature of anomalous monism is the normative character of mental descriptions. To attribute beliefs and desires is, for Davidson, to situate an agent within a framework of rationality—coherence, consistency, and responsiveness to evidence. This interpretive framework, he argues, cannot be fully captured by the syntactic form of strict laws.

Some philosophers welcome this as a defense of the autonomy of the mental: mental descriptions track norms and reasons, not merely regularities of behavior. Others respond that while strict laws may be absent, there might still be probabilistic or ceteris paribus psychophysical laws compatible with rational holism, challenging Davidson’s stark anomalism.

4. Relation to Other Mind–Body Theories
Anomalous monism has been contrasted with:

• Type-type identity theory, which posits strict correlations between mental and brain state types;
• Functionalism, which defines mental states by their causal roles, often in terms of input–output and internal relations;
• Property dualism, which allows non-physical mental properties even if they are realized in the brain.

Where property dualists emphasize ontological distinctness and many non-reductive physicalists emphasize property-level autonomy, anomalous monism emphasizes event-level identity coupled with vocabulary-level irreducibility. This distinctive configuration has made it a focal point for assessing how far physicalism can be reconciled with everyday and scientific talk about the mental.

Overall, anomalous monism remains a pivotal theory in analytic philosophy of mind, shaping ongoing debates about how to reconcile physicalism, mental causation, and the special character of psychological explanation without collapsing into either reductive materialism or dualism.