21 Modal logic and philosophy

Abstract

Publisher Summary Modal logic was born in philosophy, and has travelled widely; it retains important links with the discipline. This chapter discusses the historical heartland of philosophical modal logic—namely, the scope and limitations of modal logic as an account of necessity and possibility. It also examines modal logic and the logic of belief change, and modal logic as logic of action. The relationship between the logical and metaphysical interpretation of the alethic modalities is discussed. The epistemic logic and deontic logic are meant to illustrate two different uses that modal logic or indeed any logic can have: it may be applied to already existing (non-logical) theory, or it can be used to develop new theory. Modal logic is brought to bear on an area that has already reached a degree of maturity and that is formulated with little or no regard to modal logic. There is a strong connection between the theory of belief change and the logic of conditionals.