This Article, which is part of a larger project on the competing merits of cost-benefit analysis (CBA) and the precautionary principle (PP) as competing policymaking paradigms for environmental, health, and safety regulation, examines one specific plank of the case against the PP: the claim that the principle\u27s ignorance of the opportunity costs of precaution leads to indeterminate or impoverishing policy advice. Because PP defenders emphasize the limits of human knowledge and the frequency of unpleasant surprises from technology and industrial development, they prefer an ex ante stance of precaution whenever a proposed activity meets some threshold possibility of causing severe harm to human health or the environment. Importantly, they ...