Moral Desirability and Rational Decision

Being a formal and general as well as the most widely accepted approach to practical rationality, rational decision theory should be crucial for justifying rational morals. In particular, acting morally should also (nearly always) be rational in decision theoretic terms. After defending this thesis, in the critical part of the paper two strategies to develop morals following this insight are criticized: game theoretical ethics of cooperation and ethical intuitionism. The central structural objections to ethics of cooperation are that they too directly aim at the rationality of moral action and that they to do not encompass moral values or a moral desirability function. The constructive half of the paper takes up these criticisms by developing a two-part strategy to bring rationality and morals in line. The first part is to define ‘moral desirability’. This is done, using multi-attribute utility theory, by equating several adequate components of an individual’s comprehensive (rational) utility function with the moral desirability function. The second part is to introduce mechanisms, institutions, in particular socially valid moral norms, that provide further motivation for acting in accordance with morals.