Choices can be wise or foolish, and feelings can be apt or off the mark. So we judge, and it would be good to know what content these normative judgements carry. Gibbard offers an answer, and elaborates it. His theory explores what is at issue in narrowly moral questions, and in questions of rational thought and conduct in general.

In this paper I offer an account of the meaning of must and can within the framework of possible worlds semantics. The paper consists of two parts: the first argues for a relative concept of modality underlying modal words like must and can in natural language. I give preliminary definitions of the meaning of these words which are formulated in terms of logical consequence and compatibility, respectively. The second part discusses one kind of insufficiency in the meaning definitions given in (...) the first part, which arise from the ex falso quodlibet paradox of logical consequence. In stepwise fashion, I make an attempt to avoid most of the consequences of this paradox for the meaning definitions of must and can. (shrink)

This book examines some of the deepest questions in philosophy: What is involved in judging a belief, action, or feeling to be rational?