This volume is focused on the dynamics of reasoning processes. It covers both the topics of the dynamics of reasoning, where reasoning is viewed as a process, and reasoning about dynamics, which must be understood as pertaining to how both designers of, and agents within dynamic systems may reason about these systems. In this volume real-life applications of the modelling techniques are also considered, as the research during the DRUMS (Defeasible Reasoning and Uncertainty Management Systems) project was aimed at bridging the gap between theory and practice. In order to give the book a broader perspective, a number of well-known researchers outside the project but working on similar topics, have been invited to contribute.