epiphenomena

Epiphenomena are phenomena that occur as byproducts of a primary process but do not themselves influence that process. In the philosophy of mind, epiphenomenalism is the view that mental states—such as feelings, thoughts, and desires—are byproducts of brain activity and do not causally affect physical brain states or behavior. Under this view, all behavior is governed by physical processes in the brain, while subjective experience simply accompanies these processes without steering them.

Epiphenomenalism is one stance in the larger mind–body discussion, seeking to preserve a causal closure of the physical while explaining the reliable correlation between mental states and brain states. It contrasts with interactionist dualism, which maintains that mental and physical realms can causally affect each other, and with various forms of reductionism or emergentism that attribute some form of causal efficacy to higher-level states.

Critics argue that epiphenomenalism faces significant challenges, notably how mental states could consistently correlate with brain states if they do not influence behavior or physiology. It also raises issues for introspection, intention, and concepts such as free will. Some philosophers pursue alternative accounts, including more nuanced forms of mental causation or eliminativist positions that question the existence of certain mental states as ordinarily conceived.

Beyond philosophy, the term epiphenomenon is used in science to describe a secondary, incidental effect that accompanies a primary process without driving it, illustrating how complex systems can generate byproducts that lack causal influence on the process itself.