The Supreme Court ordinarily supports its establishment of major constitutional principles with detailed justifications in its opinions. On occasion, however, the Court proceeds in a very different way, issuing landmark pronouncements without giving any supportive reasons at all. This Article documents the recurring character and deep importance of these “quietrevolution rulings” in constitutional law. It shows that—however surprising it might seem—rulings of this sort have played key roles in shaping incorporation; reverse incorporation; congressional power; federal courts; and freedom-ofspeech, freedom-of-religion, and equal-protection law. According to the synthesis offered here, these rulings fall into two categories. One set of cases involves “ipse dixit declarations,” which establish major hornbook-type principles even while offering no reasons on their behalf. In the other group of cases—characterized here as “invitational pronouncements”—the Court does not establish discrete constitutional doctrines but instead deploys rhetoric that sets the stage for transformative future developments. This Article explores the nature and justifiability of quiet-revolution rulings. It posits that recent developments may well steer the Court away from the future issuance of decisions of this kind. Such a result will appeal to observers who view the law as centered on careful reason-giving. Even so, it may be that the issuance of quiet-revolution rulings sometimes makes good sense. Especially for analysts drawn to common-law constitutionalism, invitational pronouncements may hold value because they signal possible pathways for developing the law over time. In unusual cases, ipse dixit declarations may do helpful work, too. In particular, the Court sometimes faces the unwelcome prospect of deciding a case through the issuance of a confusing mix of plurality opinions. In these instances, the option of issuing an ipse dixit declaration may allow a majority of the Court to come together in a single opinion, thus allowing it to bring needed clarity to the law.