 The irrelevance of causation to the giving of efficient incentives has left economists struggling to make sense of the cause-in-fact requirement of criminal law and tort liability rules. Since no metaphysical reading of “cause” is appropriate to the goal of efficiency, some policy calculus is given as the legal meaning of “cause”. Such policy calculus typically generates a probabilistic interpretation of “cause”, so that any activity that raises the conditional probability of some harm that has occurred is said to have “caused” that harm (Calabresi 1975). For any theory seeking to use the law to give incentives to efficient behavior in a world of high transaction costs, this probabilistic interpretation is seemingly just what is required. To criticize such probabilistic interpretation of legal cause on the ground that probability is a poor metaphysical account of what causation is (Wright 1985a, 1987), would thus be beside the point—so long as one adheres to the economists’ utilitarian views about the proper function of the concept of causation in the law.