The history of law is in no small part the history of its boundaries. And the history of legal theory, or jurisprudence more narrowly,1 is thus a history of exploring, analyzing, and debating these boundaries. Indeed, as far back as 1906, in a tribute to the then–recently deceased Christopher Columbus Langdell, Joseph Beale recalled that many of Langdell’s students complained that his teaching, which tended to focus on older decisions from England rather than on general rules from treatises or newer American cases, “was not law.”2
Seen through 2017 eyes, the student complaint that decisions by English judges on topics such as mortgages and specific performance of contracts were not law seems bizarre. What could be more law, we might now think, than an analysis of the holdings of English courts on the subjects just mentioned, or on, say, suretyship? But to the students who carped about Langdell’s obsession with matters ancient and English, law was something narrower. For them law was constituted by general principles as stated in authoritative treatises and perhaps by currently controlling decisions (and, presumably, statutes, and various other sources of legal doctrine) of the jurisdiction within which they lived and where they intended to practice. Everything else, we suspect, was for them mere archaeology, history, or antiquarianism, none of which had a proper place in a school of law.
The anecdote is instructive. Because law is not simply the sum total of all the rules, principles, procedures, norms, and institutions that are present throughout society at large,3 it follows that there are sources of normative guidance and factual enlightenment that legitimately exist in the wider society but that are nevertheless no part of law.4
Even this modest claim, however, presupposes a boundary between law and not-law, in much the same way that institutions such as law schools, law libraries, and bar examinations presuppose much the same thing. But the boundary between law and not-law is a shifting one, as our contemporary reaction to the complaints of Langdell’s students indicates. The shift has not been unidirectional, and the boundaries of law, even if generally wider now than at most times in the past, still seem at some times to expand and at other times to contract. Yet although the boundaries between law and not-law are not stable, they remain no less important in delineating the character of law, legal argument, and legal decisionmaking. To know what law is, after all, requires that one know what law is not.
It is not surprising, therefore, that most of the important debates in jurisprudence over the past 200 years have been about the boundaries of law, and about the extent to which what some have thought of as non-law is, or has become, law, and occasionally about the extent to which what some have thought of as law is not really law at all. Law is a source-based enterprise, and understanding its nature accordingly requires understanding which sources constitute the law and which do not. It is only to be expected, therefore, that jurisprudential debates about the nature of law are so often debates about which sources of decisional guidance are to be treated as law — what counts as law. Examining these debates, many of them closely connected to the Harvard Law School, will tell us much about the boundaries of law, and thus about law itself.
* David and Mary Harrison Distinguished Professor of Law, University of Virginia. I have benefited greatly from the perceptive comments of Charles Barzun, Dan Coquillette, Bruce Kimball, Nicoletta Ladavac, John Manning, Martha Minow, Dan Ortiz, Stanley Paulson, Dan Priel, Kristen Rundle, Sophie Papaefthymiou, Adrian Vermeule, Kevin Walton, Ted White, and Kenneth Winston; from valuable snippets of information offered by numerous friends and colleagues; from the facilities and hospitality of the University of Sydney Law School; and from audience questions at L’École de Droit, Sciences Po, Paris.