Causation is a profound problem. We could think about it for years and perhaps at the end be little closer to understanding it. Yet one of the majesties of the law is that it must answer the unanswerable: It must decide, today, between plaintiff and defendant, and lacks the luxury of indefinite speculation. Consequently, judges must settle for some working approaches to thorny problems like causation, approaches that are no doubt imperfect, perhaps not even fully intellectually consistent, and always subject to refinement and eventual change.