Rethinking the Precautionary Principle and Its Role in Climate Change Policy

The precautionary principle has appeared in numerous environmental laws and declarations and has become common in discussions of environmental challenges. It captures the intuition that it is better to be safe than sorry. The primary aim of this dissertation is to identify what role the precautionary principle should play in climate change policy. This requires offering an interpretation of the precautionary principle that overcomes the challenges this principle has been accused of facing. In its most general formulations the precautionary principle states that when there is a threat of harm to human health (and/or the environment) precautionary measures ought to be taken to prevent said harm even if there is uncertainty about its extent or nature. There are many different interpretations, however, of both the nature and content of the precautionary principle. Some think of the precautionary principle as a family of principles with a shared structure and/or aim; some think of it as a way of approaching decision-making in the face of uncertainty; some think of it as a combination of these. The many ways in which the precautionary principle's components are unclear make formulating a single plausible "precautionary principle" especially challenging. I argue that rather than thinking of the precautionary principle as a loose family of principles that share a common structure or as a decision-making procedure, we should recognize that "better safe than sorry" cannot universally justify precautionary action. Nonetheless, there are some cases in which we ought to take such measures. I defend the Catastrophe Precautionary Principle, which says we ought to take appropriate precautionary measures against threats of catastrophe. The challenges of decision-making under conditions of uncertainty necessitate a Precautionary Decision-Making Framework in order to understand what a Precautionary Principle (e.g. the Catastrophe Precautionary Principle) requires of us. The distinction will allow us to both resolve confusion concerning the nature of "the precautionary principle" and allow the lack of clarity to be resolved on a case-by-case basis. Further, contrary to many recent arguments, including those of Cass Sunstein, I argue that cost-benefit analysis cannot supplant the Catastrophe Precautionary Principle. The Precautionary Decision-Making Framework has two aims. The first aim is to guide us to understand threats of harm and whether a specific threat meets the Catastrophe Precautionary Principle's criteria. It requires us to assess a threat of harm by taking into account: all available sources of information; uncertainties in knowledge; and whether we have good reason that the threat of harm is in fact a threat of catastrophe (but requires only this very low standard of evidence). The second aim of the Precautionary Decision-Making Framework aims to guide us to determine an appropriate course of precautionary action for addressing a threat of harm that has been deemed to require or warrant precautionary measures. It requires us to identify: causation and potential outcomes; likelihood; available precautionary measures; whether there are any thresholds for effective precautionary action; which of the available precautionary measures are appropriate for addressing the threat of harm; specific actors who should be held responsible for taking the prescribed precautionary measures; and whether there are any other relevant normative considerations that should be taken into account when implementing the proposed plan of precautionary action. I argue throughout the dissertation that climate change is a paradigmatic case of a complex phenomenon...