 The fusion of a basic preference/deontic setting and epistemic logic provides basic formal tools to discuss the epistemic aspects of preferences and obligations. For example, consider the  paradox of epistemic obligation:  a bank is being robbed (r), and the guards ought to know about the robbery \((OKr)\). But knowledge is factive \((Kr \rightarrow r)\), so then the bank ought to be robbed \((Or)\)! More on these concerns (under different formal systems) can be found within the discussion on knowledge and obligations  (section 4.8).