Logic deals with the fundamental notions of truth and falsity.
Modal logic arose from the philosophical study of modes of truth with the two most common modes being necessarily true and possibly true.
Nowadays modal logic is used to reason about knowledge, about obligations, about programs and about time, among others.
Actual research in modal logic spans philosophy, computer science and mathematics using techniques from relational structures, universal algebra, topology, an.
College Publications Advances in modal logic, volume 13, paperback/nicola olivetti
