Introduction

Progress has always brought, along with rosy prospects, shadowy perils. The risky byproducts of technology, combined with an enhanced appreciation of hazards, is making us edgier than ever. The "precautionary principle" is being widely proposed as a response. The term has come to be routinely included in multilateral environmental agreements and declarations,¹ and is also appearing in local laws² and scattered judicial opinions.³ Notoriously, however, "the" precautionary principle's meaning—or "meanings," for it has been put forth in so many versions, often with cognate phrasing,⁴ as to belie the pretensions of the definite article—remains obscure.

The United Nations' General Assembly Resolutionon the World Charter for Nature (1982), in addressing "activities which are likely to pose a significant risk to nature," declares that "where potential adverse effects are not fully understood, the activities shall not proceed."⁵ But of course the adverse effects of activities are never "fully understood"; taken literally, the directive would be: "Don't do anything."