This volume tackles the nature and normativity of defeat, as well as its relation to other important normative notions, such as knowledge, reasons, and justification. Traditionally, the notion of defeat has been central to epistemology, practical reasoning, and ethics. Justification, be it moral, practical, or epistemic, is widely thought to be defeasible, in that it can be undermined or undercut. This section does two things; first, it surveys the extant literature on defeat, by focusing, in particular, on debates about the nature and extent of defeat, as well as work on kinds of defeaters. Second, we give brief overview of each chapter of the volume in turn.