Contributor(s): Evelyn Fox Keller | 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 based 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 provide a more trustworthy basis for decision making. Evelyn Fox KellerEvelyn Fox Keller is Professor of the History and Philosophy of Science at the Massachusetts Institute of Technology. Her research focuses on the history and philosophy of modern biology and on gender and science. She is the author of several books, including A Feeling for the Organism: The Life and Work of Barbara McClintock (1983), Reflections on Gender and Science (1985), The Century of the Gene (2000), and Making Sense of Life: Explaining Biological Development with Models, Metaphors and Machines (2002). Her most recent book, The Mirage of a Space Between Nature and Nuture, is now in press.