The non-reductive physicalist would like to believe that mental properties are not identical to physical properties; that there are complete causal explanations of all events in terms of physical properties; and that there are sometimes explanations of events in terms of mental properties. However, some have argued that these claims cannot all be true, since they are collectively inconsistent with a principle of causal exclusion. In this paper I argue that the best formulation of the interventionist theory of causation entails (...) the falsity of the exclusion principle. However, I argue that it does so at the cost of revealing a weakness in the interventionist theory itself. (shrink)