 This Pigouvian view of tort law has given way to the post-1960 view of Ronald Coase: tort law indeed exists in order to achieve an efficient allocation of resources, yet such efficiency will be achieved whether tort liability tracks causal responsibility or not. Coase’s essential insight was that to economically rational actors opportunity costs are real costs too, so that a forgone opportunity to accept a payment in lieu of causing another person some harm already forces the harm-causer to “internalize” all costs of his activities. Such a harm-causer need not be liable for such harms in order to have him pay for the “true costs” of his activity; he already “pays” by forgoing the opportunity to be bought off by the sufferer of the harm. As each harm-causer and harm-sufferer decides on the desired level of his activity, he will thus take into account all effects of his interaction without a cause-based tort liability forcing him to do so (Coase 1960).