Rationality, utility and deontic reasoning

In this chapter, we are interested in one extremely important type of deontic reasoning, which takes place when people try to find out which actions they ought to perform or may perform. This type of reasoning has traditionally, in philosophy, been called ‘practical reasoning’ and distinguished from ‘theoretical reasoning’, which has the object of trying to discover, or to describe correctly, objective matters of fact. It is sometimes said that the difference between these two is that between trying to infer what one should (or may) do as opposed to trying to infer what one should (or may) believe. The latter does not have to be ‘theoretical’ in the scientific sense, and could be directed towards ordinary…