From The Art and Popular Culture Encyclopedia
"Since the epiphenomenon is often equated with the accident, pataphysics will be above all the science of the particular, even though it is said that science deals only with the general." --Exploits and Opinions of Dr. Faustroll, Pataphysician (1911) by Alfred Jarry
An epiphenomenon (plural - epiphenomena) is a secondary phenomenon that occurs alongside or in parallel to a primary phenomenon.
Examples of epiphenomena
Epiphenomena in medicine
In medicine, an epiphenomenon is a secondary symptom seemingly unrelated to the original disease or disorder. For example, having an increased risk of breast cancer as a result of taking an antibiotic is an epiphenomenon. It is not the antibiotic that is causing the increased risk, but the increased inflammation associated with bacterial infection.
In the more general use of the word a causal relationship between the phenomena is implied: the epiphenomenon is a consequence of the primary phenomenon; however, in medicine this relationship is typically not implied: an epiphenomenon may occur independently, and is merely called an epiphenomenon because it is not the primary phenomenon under study. (A side-effect is a specific kind of epiphenomenon that does occur as a direct consequence.)
Epiphenomena in philosophy of mind and psychology
An epiphenomenon can be an effect of primary phenomena, but cannot affect a primary phenomenon. In philosophy of mind, epiphenomenalism is the view that mental phenomena are epiphenomena in that they can be caused by physical phenomena, but cannot cause physical phenomena. In strong epiphenomenalism, epiphenomena that are mental phenomena can only be caused by physical phenomena, not by other mental phenomena. In weak epiphenomenalism, epiphenomena that are mental phenomena can be caused by both physical phenomena and other mental phenomena, but mental phenomena cannot be the cause of any physical phenomenon.
The physical world operates independently of the mental world in epiphenomenalism; the mental world exists as a derivative parallel world to the physical world, affected by the physical world (and by other epiphenomena in weak epiphenomenalism), but not able to have an effect on the physical world. Instrumentalist versions of epiphenomenalism allow some mental phenomena to cause physical phenomena, when those mental phenomena can be strictly analyzable as summaries of physical phenomena, preserving causality of the physical world to be strictly analyzable by other physical phenomena.
According to epiphenomenalism, the free will to have an effect on the physical world is an illusion, as physical phenomena can only be caused by other physical phenomena. In weak epiphenomenalism, there is free will to cause some mental effects, allowing for mental discipline that is directed at other mental phenomena, or some new age effects on the mind.
Weak versions of behaviorism in psychology, which admit for the existence of mental phenomena, but not to their meaningful study as causes of any observable behavior in psychology, view mental phenomena as either epiphenomena, or linguistic summaries, as instrumentalist tools for examination of objectively observable physical behavior in others.
History of the term
Epiphenomenalism was mentioned by Thomas Henry Huxley as early as 1874.