One of the main difficulties with contemporary materialism is the risk of epiphenomenalism: if mental properties systematically depend on physical properties, how can they have causal efficiency? Davidson's anomalous monism' only solves this problem through a "feeble" understanding of the individuation of events and with relative imprecision as to the pertinence of causal explanations formulated in psychological terms. Nor do other conceptions of the individuation of events and the causal power of mental states, as that of Kim and of Jackson and Pettit, solve the problem. It will not then be solved by modifying the theory of the individuation of events.