The subject of decision theory under non-standard uncertainty has become increasingly pertinent in many disciplines today. This volume provides a comprehensive assessment of the concepts and theories developed to deal with situations in which standard tools of decision theory cannot be used. It moves beyond the classical distinction between risk and uncertainty, and suggests that most problems involving strategic choices in the face of severe uncertainty involve a conceptual and methodological shift addressing the interface between quantitative and qualitative assessment. The volume takes an interdisciplinary approach and provides a coherent framework to explore fundamental uncertainty from the point of view of an extended conception of rationality. It examines topics, such as, rationality and commitment, weight of argument and probability structures, similarity theory, reasoning with natural languages, economic decisions and moral judgement in view of uncertain outcomes. This book is indispensable reading for all interested in behavioural economics and decision-making theory. "This volume addresses the subject of uncertainty from the point of view of an extended conception of rationality. In particular, the contributions explore the premises and implications of plausible reasoning when probabilities are non-measurable or unknown, and when the space of possible events is only partially identified."--Publisher description.