Taming chance: Risk and the quantification of uncertainty

The quantification of uncertainty through probability is central to definitions of risk used in environmental policy analysis. This essay explores the translation of unquantified uncertainty into probability and the expression of allied philosophical problems in the practice of environmental risk and decision analysis. First we look at means used in science for handling uncertainty associated with some major risks and which are not well represented through probability. ‘Saving the science’ without quantified probability is addressed through the role of probabilistic events in risk analysis, suggesting the need to expand the scope of risk analysis to include some types of unquantified reasoning about adverse events. Next we look at uses of subjective probability and decision analysis to overcome problems of unquantified uncertainty in science, where we argue that a constructive conception of probability judgments, based in the foundations of decision analysis, provides the most useful approach for such methods. A theme throughout is the role of intellectual control implicit in our efforts ‘to tame change’ through the representation of uncertainty through probability.