Epiphenomenalism (Dualism)

Epiphenomenalism is considered a kind of dualism—specifically a type of property dualism—because it maintains a fundamental ontological distinction between mental and physical properties. Both epiphenomenalism and dualism hold that mental phenomena are not reducible to physical processes—because conscious experiences (qualia—e.g., the “redness” of red or the feeling of pain) are non-physical in nature. This sets epiphenomenalism apart from materialist or physicalist theories (like Identity Theory), which claim that mental states are just physical brain states. Thus, epiphenomenalism is a dualist view in that it affirms that there are at least two kinds of properties in the world: mental and physical.

Epiphenomenalism posits that mental properties—consciousness and qualia—are non-physical, irreducible to brain processes, and yet caused by them.

Definition and Distinctions

Epiphenomenalism is similar to Property Dualism and Non-Reductive Physicalism in that there is only one kind of substance, material/physical substance, and all mental states or properties are caused by physical processes, but epiphenomenalism differs from property dualism and non-reductive physicalism in that epiphenomenalism‘s mental states do not cause anything in return. According to David Chalmers, “Epiphenomenalism is a version of property dualism, and like all versions of property dualism, it holds that mental properties are distinct from, and not reducible to, physical properties” (Chalmers, 1996).

History and Critiques

Epiphenomenalism emerged from dualism as scientific advances made it harder to defend substance dualism with full mind-body interaction, due to the lack of observable causal effects of mental phenomena on the physical world. Epiphenomenalism seemed to be a kind of compromise: Keep the idea that conscious experience is non-physical. But concede that it doesn’t affect physical processes—i.e., it’s just a byproduct.

Thomas Henry Huxley famously compared consciousness to the steam whistle on a locomotive: “The steam-whistle which accompanies the work of a locomotive engine is without influence upon its machinery.”

Even though epiphenomenalism denies mental-to-physical causation, and does not allow substances other than material/physical ones, it still counts as a kind of dualism, because it affirms the existence of non-physical mental properties and their distinction from physical properties. This is sufficient for it to qualify as a kind of dualism, because dualism is about ontology (what kinds of things/properties exist), not necessarily about causation.

Epiphenomenalism is also classified under Materialism, because it takes only the physical to be real, only the material brain generates consciousness.