Epiphenomenalism

Epiphenomenalism was mentioned by Thomas Henry Huxley as early as 1874.^[2]

http://en.wikipedia.org/wiki/Epiphenomenon
http://plato.stanford.edu/entries/epiphenomenalism/
An epiphenomenon (plural - epiphenomena) is a secondary phenomenon that occurs alongside or in parallel to a primary phenomenon.

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 concurrent with taking anantibiotic is an epiphenomenon. It is not the antibiotic that is causing the increased risk, but the increased inflammation associated with bacterial infection.

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.

Huxley (1874), who held the view, compared mental events to a steam whistle that contributes nothing to the work of a locomotive. James (1879), who rejected the view, characterized epiphenomenalists' mental events as not affecting the brain activity that produces them “any more than a shadow reacts upon the steps of the traveller whom it accompanies”.