 One may try to rescue mental efficacy by supposing that whenever there is a mental effect in the physical world there is also a physical force that is a sufficient cause of the effect. This view, however, both offends Occamist principles and fails to satisfy the leading anti-epiphenomenalist intuition, namely, that the mental makes a difference to the physical, i.e., that it leads to behavior that would not have happened in absence of the mental. The view also leads to an epistemological problem: If there is always a sufficient physical cause for whatever a mental event is supposed to produce, then one could never be in a position where one needs to suppose there is anything non-physical at work, and thus there could never be any reason to introduce mental causes into one’s account of neural events or behavior.