In at least some of their forms, Cost-Benefit techniques for the evaluation of environmental projects and policies treat the preferences of citizens as the sole determinants of the value of outcomes. There are two salient ways in which this supposition might be defended. The first is metaethical and appeals to considerations about how we must understand talk of environmental and other values. The second is political and appeals to considerations about democratic legitimacy and the proper aims of public policy. Metaethical (...) considerations, I argue, are something of a red herring here. Roughly subjectivist understandings of our talk of values may be appealingly metaphysically unassuming, but in their most plausible formulations they do not support a view of preferences as the sole determinants of value. Political considerations, on the other hand, are to be taken very seriously. They offer, however, no straightforward rationale for any crudely preferentialist measure of social value. Findings obtained from the use of cost-benefit techniques might sometimes have a legitimate role as an input into, but not as a substitute for, political deliberation. Questions about the scope and limits of such legitimacy are properly addressed in political and not in metaethical terms. (shrink)