Abstract: In 2013, the Supreme Court showed an unusually high rate of unanimous decisions – the highest, in fact, since 1940. This increase in unanimity, long favored by Chief Justice John Roberts, places a spotlight on an insufficiently appreciated fact: In 1941, the Supreme Court experienced a radical transformation. Almost immediately, it changed from a court that had operated by consensus, with very few separate opinions, into something closer to nine separate law offices, with a large number of dissenting opinions and concurrences, and with a significant rate of 5-4 divisions. Remarkably, the patterns established in the early 1800s continued until 1941, and the patterns established in the early 1940s have persisted to the present day. The transformation of 1941 appears to be attributable, in significant part, to the leadership style of Chief Justice Harlan Fiske Stone, who had no aversion to separate opinions and split decisions, and who was a frequent dissenter himself. The transformation offers general lessons not only about consensus and dissent within courts, but also about broader relationships among leaders, personnel, path dependence, prevailing norms, and the Court’s future. With respect to group behavior, it suggests the possibility of multiple equilibria: With small differences in leadership style and prevailing norms, the level of publicly expressed dissent can either grow or wither. With respect to the normative issues, the standard arguments in favor of a higher level of consensus within the Court – pointing to the values of legitimacy, stability, and minimalism – rest on fragile empirical foundations. It is true that a badly fractured Supreme Court can create uncertainty, and that internal divisions have costs as well as benefits, but there is no sufficient reason to hope for a return to the pre-1941 patterns.