I argue for the epiphenomenality of functional properties by means of thought experiments and general principles. General principles suggest that an object’s causal powers nomologically supervene on its intrinsic properties and that its functional role does not. This implies that it is possible for an object to lose its functional role without undergoing any change to its intrinsic properties or causal powers. Nor is it difficult to conceive of such scenarios. Various thought experiments are introduced for just this purpose. But (...) properties that can vary independently of an object’s causal powers in this way are epiphenomenal, for their instantiation by an object at a time makes no difference to the causal processes the object is involved in at that time. The same processes would have occurred even if such properties hadn’t been instantiated. The intrinsicness thesis is controversial, but it is not controversial that it is true of productive causation, and many believe that productive causation is the only form of mental causation worth having. Nevertheless, in the paper’s final section I consider dependence-based accounts of causation, which do not presuppose the intrinsicness of causal powers, and show that they too have difficulties accounting for the efficacy of functional properties. (shrink)