‘The definitive version is available at www.blackwell-synergy.com '. Copyright Blackwell Publishing. DOI: 10.1111/j.1746-8361.1998.tb00040.x [Full text of this article is not available in the UHRA]Professor Davidson's anomalous monism has been subject to the criticism that, despite advertisements to the contrary, if it were true mental properties would be epiphenomenal. To this Davidson has replied that his critics have misunderstood his views concerning the extensional nature of causal relations and the intensional character of causal explanations. I call this his ‘extension reply’. This paper argues that there are two ways to read Davidson's ‘extension reply’; one weaker and one stronger. But the dilemma is that: (i) the weak extension re...