This is a new edition of Gardenfors' classic text, presented to the community with a Foreword by David Makinson and an appendix containing a paper "Relations between the logic of theory change and nonmonotonic logic" by the author and David Makinson. The following describes the first edition: Knowledge in Flux presents a theory of rational changes of belief, focusing on revisions that occur when the agent receives new information that is inconsistent with the present epistemic state. It brings together, systematises and enlarges upon an already influential body of work by the author and his...