Argument about causation inside and outside the law is often concerned with the following question: Must a cause be a necessary condition of a result, a sufficient condition of the result, or a necessary element in a set of conditions jointly sufficient to produce the result? This essay supports the third view, both outside the law and inside it, whenever a sequence of physical events is in issue. The article argues that there is no special 'legal' meaning of causation, since the same concept of cause is used for discovering recipes, for explaining events, and for assigning responsibility for outcomes. The normative elements are supplied by substantive tort law, which defines the conduct that entails or may entail tort liability and prescribes when causal connection between conduct and harm must be proved.