Abstract: This article examines precautionary strategies of constitutional design and interpretation. In many contexts, constitutional actors and theorists justify rules of constitutional law as precautionary measures against various political risks, including the abuse of power by incumbent officials, dictatorship, majoritarian oppression, and biased adjudication. After providing an analytic taxonomy of such arguments, I examine criticisms of constitutional precautions offered by early proponents of national power such as Hamilton, Marshall and Story, and by New Dealers such as Frankfurter and Jackson. These critics argued that precautionary constitutionalism might be futile, might jeopardize other values, and might even prove perversely self-defeating, if and because the precautions create or exacerbate the very risks they were intended to prevent. Accordingly, these critics argued for a “mature position” that requires constitutional rulemakers to consider all relevant risks of action and of inaction. I identify a strictly negative but nonetheless valuable function of that approach: by laundering out one-sided arguments and placing all relevant risks before constitutional rulemakers, the mature position improves the process of constitutional design and interpretation.