Alan Ross Anderson was one of the first logicians who were interested in the logic of prudence and related concepts, such as caution. He called this area “eubouliatic logic,” a term which has not become popular. Anderson made a distinction between four prudence-related concepts which can be placed in a square of opposition. Prudence and related concepts are nowadays often seen as fuzzy concepts. We investigate which consequences this has for the logic of these concepts.

Some years ago, Lokhorst proposed an intuitionistic reformulation of Mally's deontic logic (1926). This reformulation was unsatisfactory, because it provided a striking theorem that Mally himself did not mention. In this paper, we present an alternative reformulation of Mally's deontic logic that does not provide this theorem.