Compatibilists aim to solve the causal exclusion problem by arguing that a physical cause and a mental cause are compatible with each other without involving the problematic overdetermination. The purpose of this paper is twofold. First, I target at Karen Bennett’s (2003, 2008) influential compatibilist strategy—one that rests on the assumption that a mental cause is sufficient for bringing about a physical effect, just as a physical cause is. I argue that, on a plausible physicalist picture, this assumption cannot be (...) established. Second, I propose a weaker and more plausible interpretation of the mental efficacy, which takes a mental cause to be necessary (but not sufficient) for a physical effect in a counterfactual sense. The resulting picture of mental causation avoids the difficulties engendered from Bennett’s assumption and delivers fresh resources to solve the exclusion problem. (shrink)