1.NounThe doctrine that consciousness, mental states and processes are simply by-products of physiological events in the brain or nervous system and cannot themselves cause anything, whether material or immaterial. .mw-parser-output .defdate{font-size:smaller}
"In the eyes of epiphenomenalism, anger does not cause one to shout nor does grief cause one to cry; the feelings are by-products of the underlying physical causes and nothing more."
2.NounSuch a doctrine, as advanced by a particular thinker or school of thought.