The Limits of Cost-Benefit Calculation: Commentary on Bennis, Medin, & Bartels (2010)

Bennis, Medin, and Bartels (2010, this issue) correctly identify real limits to the efficacy of cost-benefit analysis in comparison to moral rules. In this commentary, I suggest that those very same limits apply to decision making in general. Cost-benefit analysis may be the best way to arrive at decisions under a set of "closed-world assumptions" like those described by Bennis et al. But those assumptions virtually never hold, and in the absence of those assumptions, cost-benefit analysis often substitutes counting for thinking.