Résumé
In the United States and most industrialized countries, regulatory policies pertaining to food safety, occupational health, and environmental protection are (according to laws and statutes) science based. The complexity of some ecosystems and new technologies, however, makes it increasingly necessary to deal with situations where scientists cannot yet provide a definite picture. In this context, a widely invoked (but debated) rule, known as the Precautionary Principle, says to address potential hazards right away with preventive measures. We develop an intuitive formalization of this rule, which allows us to infer what an appropriate precautionary policy should do. Implications for resource conservation and the regulation of technological risks are then explored.