A note on knowledge-first decision theory and practical adequacy

According to Williamson (2000), your evidence at a given time is given by all the propositions you know at that time. According to traditional decision theory, in figuring out what to do you should consider all the states that are compatible with your evidence. The combination of the two views, knowledge-first decision theory, has it then that in figuring out what to do you should consider all and only those states compatible with what you know. If knowledge by inductive inference is possible, however, knowledgefirst decision theory would have you rule out for considerations states which you shouldn’t rule out. In this note, I first present this problem for knowledge-first decision theory, and then suggest a fix for it based on the idea that a proposition cannot be known unless it is practically adequate.