 The conventional wisdom about the causation requirement in both criminal law and torts is that it in reality consists of two very different requirements for liability. The first requirement is that of “cause in fact”. Such conventional wisdom holds that the “cause-in-fact” requirement is the only truly causal component of the law’s two requirements (despite the fact that both are framed in causal terms), because this doctrine is the only one that corresponds with any scientific or even factual notion of causation. Whether cigarette smoking causes cancer, whether the presence of hydrogen or helium caused an explosion, are factual questions to be resolved by the best science the courts can muster, and these are classed as “cause-in-fact” questions. By contrast, it is contested whether the second requirement, that of “proximate” or “legal” cause, is an evaluative issue, to be resolved by arguments of policy, or whether it too is a matter of causal fact. Suppose a defendant knifes his victim, who then dies because her religious convictions are such that she refuses medical treatment while knowing that such refusal will kill her (Regina v. Blaue). Has such a defendant (legally) caused her death? The doctrines of proximate cause are used to resolve such questions, it being controversial whether such resolutions are matters of natural fact or of moral fact (“policy”).