The doctrine of precedent is one of the most distinctive features of the modern common law. Understanding the operation of precedent is important for our theorizing about the nature of law, since any adequate theory must be compatible with the practice. In this paper I will explore the conventional view of precedent endorsed by practitioners and many legal philosophers alike. I will argue that for all its attractions, it provides a distorted view of the nature of precedent. The distortion grows out of the basic assumption that precedents create rules, and thus that the common law can be understood as a form of rule-based decision-making. Instead, the common law is a form of case-by-case decision-making, and the doctrine of precedent constrains this decision-making by requiring later courts to treat earlier cases as correctly decided. The relevance of earlier cases is not well understood in terms of rules—they are better understood as a special type of reason.

It is a familiar slogan in legal circles that “like cases should be treated alike.” This idea is often confused with two others: the rationale of analogical reasoning in adjudication, and the value of coherence. I would like to keep these three issues separate, at least for a while. What is unique about idea of treating like cases alike? I would suggest that the interesting cases (and by “cases,” I do mean judicial decisions, to which this essay is confined) are those in which legal decisions are not entirely determined by reasons. If two similar cases are actually determined by the reasons that apply to them, then there is no need for the principle of treating like cases alike: The determining reasons would do all the work of justifying similar rulings. This is what makes the principle of treating like cases alike uniquely problematic and separate from the questions of analogical reasoning and coherence. In analogical reasoning, for example, the assumption is that if there is a good reason that determines a decision X under circumstances C1, and we now face a similar case C2, then the reason that determines X in C1 may also determine (or support) the decision X under C2. In other words, analogical reasoning typically appeals to the reasons that underlie the previous decision(s) and extends the application of those reasons to the new case. (I will qualify this account of analogy in the last section.)

The last decade has seen a resurgence of interest among philosophers in the core questions of ethics and justice on the international plane. Issues once discussed primarily in the response to the major global debates of the 1960s and 1970s—the Vietnam War and the North-South economic imbalance—have returned to the domain of philosophers. This engagement has taken place in two distinct but related debates. First, philosophers have devoted attention to the ethical significance of nationality and patriotism, asking whether an impartial morality permits disparate treatment of an individual's co-nationals. Second, scholars have revisited issues of international justice in great detail, including works on human rights as well as just war theory. These works ask, as Brian Barry put it, “given a world that is made up of states, what is the morally permissible range of diversity among them?” One impetus for renewed work on these ideas was the publication of John Rawls's The Law of Peoples.