Program II proposals are approved with the understanding that you will regard your core courses--generally 14-16 but no more than 18 courses--as specific graduation requirements. If it becomes necessary for you to make a course change because, for instance, one of your core courses is no longer offered at Duke, you must propose a substitute course in writing to your advisor, who will need to approve the substitution and notify the Program II office of the change before the end of drop/add in the semester in which you would be taking the substitute course. You are generally expected to substitute a course that covers some of the same material as the course being replaced. If your advisor has approved substitutes for two core courses, any additional requests to change a core course will require approval by the Program II committee.