Abstract: The Supreme Court’s increasing use of science and social science in its decision making has a rationalizing effect on law that helps ensure that a rule will have its desired effect. But resting doctrine on the shifting sands of scientific and social scientific opinion endangers legal stability. The Court must be responsive, but not reactive, to new scientific findings and theories, a difficult balance for lay justices to strike. This Article argues that the Court uses delay—defined as refusing to make or change a rule in light of new scientific arguments at time one, and then making or changing the rule because of the same arguments at time two—as a tool to improve decision making amidst scientific uncertainty. Using the Court’s antitrust jurisprudence as an example, this Article shows that delay can have a salutary effect on rulemaking because it allows the Court to use academic consensus (that either develops or matures between times one and two) as a signal of scientific reliability. As a conservatizing device, delay operates in the common law tradition, but it also avoids some of the failures associated with traditional common law features like stare decisis and incrementalism. The Article concludes by contrasting Supreme Court decision making with an area of law where delay is impractical or undesirable. In toxic tort litigation, where the goals of deterrence and compensation preclude the use of delay in the face of new scientific arguments, the law pays the price in uncertainty and error.