Introduces the most philosophically relevant kind of logic that builds on PHIL 2440. Modal logic is the logic of the concepts of necessity, possibility, and contingency. A variety of systems of sentential modal logic will be covered, along with the standard system of first-order modal logic. Recommended prereq., PHIL 2440. Same as PHIL 5460. Prerequisites: Restricted to students with 57-180 credits (Juniors or Seniors).