Langdell is a helpful example of the uneasy relationship of natural law and positivism in late-nineteenth-century accounts of common law. Some commentators treat his turn to the natural sciences as continuous with Blackstone and Story. Others herald or bemoan him as a nascent legal positivist. Langdell affirms the positive law of judges and legislators as the sole source of law, not morality or even custom, and turns to precedent to ultimately explain the particular content and binding quality of American common law. Yet, he also affirms law’s internal coherence. When students engage in the case method, he says, they find principles at the heart of the common law. In this, Langdell arguably offers an inductionist account of natural law and common law. He offers, in other words, a vision of law where more general laws or principles are formed by inference from the decisions of particular legal cases. This approach is distinct from other prominent forms of the natural-law tradition; Langdell looked to cases not principles, and the natural sciences not the mathematical. But this inductionist account is haunted by questions of justification: why should we expect to find case law reasonable? Langdell’s silence on this question allows his interpretation as either a natural lawyer or positivist. Without explicit answer to the justification question, Langdell turned to precedent. Yet he retained a belief—bolstered by his scientific method—that common law is, at its heart, reasonable.