Rule utilitarianism and decision theory

The purpose of this paper is to show how some of the controversial questions concerning utilitarianism can be clarified by the modelling techniques and the other analytical tools of decision theory (and, sometimes, of game theory). It is suggested that the moral rules of utilitarian ethics have a logical status similar to that of the normative rules (theorems) of such formal normative disciplines as decision theory and game theory. The paper argues that social utility should be defined, not in hedonistic or in ideal-utilitarian terms, but rather in terms of individual preferences, in accordance with the author's equiprobability model of moral value judgments. After describing the difficulties of act utilitarianism, rule utilitarianism is discussed as a possibly superior alternative. Brandt and Lyons have tried to show that these two forms of utilitarianism are actually equivalent. To test Brandt's and Lyons's equivalence thesis, a decision-theoretical model for utilitarian theory is proposed. The model shows that the thesis is definitely false. The basic difference between the two theories results from the expectation effect and the incentive effect, which, surprisingly enough, have been almost completely neglected in the philosophical literature. The paper illustrates these two effects in connection with the moral duty of promise keeping. Yet, even if we do neglect the expectation and the incentive effects, and concentrate on the coordination effect, as most of the philosophical literature does, it can be shown that rule utilitarianism and act utilitarianism have very different practical implications. This is demonstrated by analysis of three voting situations. Hence, the equivalence thesis fails even under the assumptions most favorable to it.