Epiphenomenalism (Stanford Encyclopedia of Philosophy)
Epiphenomenalism is the view that mental events are caused by physical
events in the brain, but have no effects upon any physical events.
Behavior is caused by muscles that contract upon receiving neural
impulses, and neural impulses are generated by input from other neurons
or from sense organs. On the epiphenomenalist view, mental events play
no causal role in this process. 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 traveler whom it accompanies”.