Metaphysical Positions
Epiphenomenalism
Mind and Body
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Epiphenomenalism holds that consciousness is real but causally inert, a byproduct thrown off by physical brain processes the way smoke is thrown off by a fire, without ever itself acting back on the physical world that produced it. Thomas Henry Huxley proposed the position in the nineteenth century, comparing conscious states to the whistle of a steam engine, present and audible but contributing nothing to the engine's actual motion. It sits between interactionism, which affirms two-way mental and physical causation, and eliminative materialism, which denies mental states are anything over and above the physical at all. The position matters because, if true, it means the felt sense of willing an action never actually causes that action, a conclusion many find nearly impossible to accept about their own deliberate choices, yet difficult to rule out by any experiment that only ever measures physical effects.
Facts
Position Profile
Earliest FormulationThomas Henry Huxley proposed the position in 1874, comparing consciousness to the whistle of a steam engine. 1 Principal ProponentThomas Henry Huxley argued that conscious states are real but causally inert byproducts of the nervous system. 1 Principal CriticWilliam James objected that epiphenomenalism makes consciousness a biologically inexplicable luxury, since natural selection could not have favored a trait with no causal effect on behavior. 1 Key TextThomas Henry Huxley's 1874 address On the Hypothesis that Animals are Automata, which compared consciousness to the whistle of a steam engine, powerless to affect the engine's workings. 1 Opposing PositionInteractionism, which affirms that mental states do cause physical effects and not only the reverse. 1 Learn More
The Steam Whistle That Does No Work
Huxley's argument for epiphenomenalism grew out of a strictly physiological picture of the nervous system: if every bodily movement can in principle be traced to a prior physical cause, a nerve impulse, a muscle contraction, then there is no causal gap left over for a mental event to fill, and consciousness, however real as an experience, must be a side effect of the physical process rather than a link in its causal chain, exactly as the whistle of a steam engine is produced by the engine's workings without itself driving the pistons.
On this picture, a person's felt decision to raise an arm and the arm's actually rising are both effects of the same prior physical brain state, running in parallel rather than one causing the other, so that the feeling of having decided is, in a precise sense, an illusion about its own causal role even though the feeling itself is perfectly real. The theory's most serious internal difficulty is sometimes called the problem of epiphenomenal qualia: if consciousness does nothing, it becomes hard to explain why evolution would have produced it at all, since natural selection can only favor traits that make some causal difference to survival and reproduction, and a purely decorative byproduct with no causal role of its own is exactly what evolutionary explanation has the hardest time accounting for.
A Position Almost No Religious Tradition Can Accept
Epiphenomenalism sits at the far end of the spectrum from nearly every religious account of mind, since a soul that causes nothing, that never actually moves the body it inhabits or answers the prayers it seems to offer, does very little of the work a soul is traditionally supposed to do; the position is consequently almost entirely a philosophical and scientific one, with essentially no religious tradition adopting it as a description of the soul, in contrast to interactionism, occasionalism, and even property dualism, each of which has genuine religious analogues. Its main philosophical rivals are interactionism, which restores full two-way causation at the cost of the interaction problem, and physicalist identity theory, which avoids the causal-inertness worry entirely by denying that mind and brain are even two things capable of one causing the other, holding instead that they are strictly identical.
Contemporary defenders of epiphenomenalism, a minority position even within analytic philosophy of mind, generally argue that it is the most honest way to take both physics, which seems to leave no causal gaps for mind to fill, and consciousness, which seems undeniably real, seriously at the same time, whatever the cost to common-sense intuitions about free deliberate action.
Cross-Tradition Connections
Affirmed By
Thomas Henry Huxley proposed epiphenomenalism in 1874, comparing consciousness to the whistle of a steam engine.
Contrasts With
Both deny mind is simply identical to brain states, but emergentism grants emergent mental properties real causal power while epiphenomenalism denies mental states cause anything physical.
Opposed By
Interactionism holds mental states cause physical effects; epiphenomenalism holds the mind never causes anything physical, only the reverse.
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