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In " Consciousness Explained " , Daniel Dennett distinguishes between a purely metaphysical sense of epiphenomenalism , in which the epiphenomenon has no causal impact at all , and Huxley 's " steam whistle " epiphenomenalism , in which effects exist but are not functionally relevant .
 Daniel Dennett, Huxley
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Answer:
 Daniel Dennett, Huxley