According to conventional wisdom, the normative source of modern tort law is mysterious. The reasons trace back to the state of nature. In a world without centralized government, individuals protected themselves by exacting talionic revenge—“an eye for an eye”—on their injurers. These customary norms of behavior were the source of the early common law, but tort scholars have assumed that they were merely a barbaric punitive practice without any relevance to the modern tort system. This field of the common law had to be normatively recreated, making it “modern.” The resultant body of tort law depends, as Oliver Wendell Holmes famously concluded, on “more or less definitely understood matters of policy.” The policies in question, however, have never been clearly identified. Courts and scholars continue to disagree about the norms that generate the behavioral obligations of modern tort law.
The normative source of modern tort law has been hidden in plain sight because of this widely held but mistaken understanding of legal history. Contrary to conventional wisdom, the state of nature was governed by a reciprocity norm of equitable balance that has survived the evolving demands of the modern tort system. In cases of accidental harm, the reciprocity norm often took the form of a compensatory obligation requiring “the value of an eye for an eye.” This norm was initially adopted and then further developed by the early common law. Courts subsequently invoked the reciprocity norm in the late nineteenth and early twentieth centuries to justify rules of negligence and strict liability. Once one looks, the importance of reciprocity is obvious.
Reciprocity, in the basic sense of “treating others like they treat you,” is a metanorm that individuals use to identify and enforce more particularized behavioral obligations in a wide variety of social interactions. Reciprocity attains equitable balance in tort cases through a series of behavioral and compensatory obligations corresponding to the modern rules of negligence and strict liability. Given the ongoing, pervasive influence of reciprocity, it readily provides the type of normative judgment that jurors must exercise when determining the behavioral requirements of reasonable care in a negligence case. Reciprocity supplies a normative practice that is distinct to tort law, defining a behavioral paradigm that normatively demarcates torts as a substantive field of the common law.
But even though tort law is distinctively defined by the paradigm of compensatory reciprocity, this normative practice does not fully justify tort law. Reciprocity is a behavioral norm. Why should the legal system enforce the norm? Must it always do so? These questions must be resolved with a substantive rationale for tort law, not with a behavioral norm that is enforced by the law.
By enforcing the behavioral obligations of reciprocity, the tort system engages in a normative practice that can be justified by the liberal egalitarian principle that each person has an equal right to autonomy or self-determination, making each responsible for the costs of his or her autonomous choices. Liberal egalitarianism is the only principle of substantive equality that can justify the tort rules that give different treatment to different types of nonreciprocal behaviors. Far from being a barbaric relic of the past, the reciprocity norm is enforced by tort law in a manner that clearly reveals the substantive rationale for this field of the common law.