This book provides a critical examination of how the choice of what to believe is represented in the standard model of belief change. In particular the use of possible worlds and infinite remainders as objects of choice is critically examined.
Descriptors are introduced as a versatile tool for expressing the success conditions of belief change, addressing both local and global descriptor revision. The book presents dynamic descriptors such as Ramsey descriptors that convey how an agent¿s beliefs tend to be changed in response to different inputs. It also explores sentential revision and demonstrates how local and global operations of revision by a sentence can be derived as a special case of descriptor revision. Lastly, the book examines revocation, a generalization of contraction in which a specified sentence is removed in a process that may possibly also involve the addition of some new information to the belief set.

Sven Ove Hansson, professor of philosophy at the Royal Institute of Technology (KTH), Stockholm, Sweden is a leading researcher in the formal modeling of belief change. In addition to his work in this area, he is also well known for his contributions to preference logic, value theory, moral philosophy, epistemology, and the philosophy of science and technology. He is the author of well over 300 articles in international refereed journals. He is the editor-in-chief of Theoria and the book series Outstanding Contributions to Logic. 

Chapter 1: The State of the Art.- Chapter 2: Inside the Black Box.- Chapter 3: Questionable Patterns of Change.- Chapter 4: Putting the Building-Blocks Together.- Chapter 5: Local Descriptor Revision.- Chapter 6: Global Descriptor Revision.- Chapter 7: Dynamic Descriptors.- Chapter 8: Sentential Revision.- Chapter 9: Revocation.- Chapter 10: Contraction.- Chapter 11: Looking Back - and Ahead.