Consequentialist Decision Theory and Utilitarian Ethics

Suppose that a social behaviour norm specifies ethical decisions at all decision nodes of every finite decision tree whose terminal nodes have consequences in a given domain. Suppose too that behaviour is both consistent in subtrees and continuous as probabilities vary. Suppose that the social consequence domain consists of profiles of individual consequences defined broadly enough so that only individuals’ random consequences should matter, and not the structure of any decision tree. Finally, suppose that each individual has a “welfare behaviour norm” coinciding with the social norm for decision trees where only that individual’s random consequences are affected by any decision. Then, after suitable normalizations, the social norm must maximize the expected value of a sum of individual welfare functions over the feasible set of random consequences. Moreover, individuals who never exist can be accorded a zero welfare level provided that any decision is acceptable on their behalf. These arguments lead to a social objective whose structural form is that of classical utilitarianism, even though individual welfare should probably be interpreted very differently from classical utility.