Assessing Risk in the Absence of Quantifiability

Abstract

A substantial literature on risk perception demonstrates the limits of human rationality, especially in the face of catastrophic risks. Human judgment, it seems, is flawed by the tendency to overestimate the magnitude of rare but evocative risks, while underestimating risks associated with commonplace dangers. Such findings are particularly relevant to the problem of crafting responsible public policy in the face of the kinds of threat posed by climate change. If the risk perception of ordinary citizens cannot be trusted, then it would seem logical to base policy decisions on expert judgment. But how rational, how trustworthy, are expert assessments of catastrophic risk? I briefly review the limitations of conventional models of expert risk analysis, especially in dealing with the large uncertainties endemic to the risk of low-probability, high-impact events in the distant future. The challenges such events pose to the underlying assumptions of these analyses are severe enough to question their basic rationality. I argue that a conception of rationality premised on the bounded knowledge of experts and lay citizens alike, based on context-appropriate heuristics, may help us in the search for a more trustworthy basis for decision making.