This book offers a collective study of issues to do with experts and expertise, a topic of tremendous contemporary significance. The perspectives are philosophical but draw on relevant work from the sciences and social sciences. In addition, in keeping with other volumes in Oxford University Press’s Engaging Philosophy series, many of the papers in the volume have an applied dimension, in that they examine the issues in practical settings. The questions discussed include the following: What is an expert? Who decides who the experts are? Should we always defer to experts? How should expertise inform public policy? What happens when the experts disagree? Must experts be unbiased? Should all experts be treated the same, or does it matter what the source of the expertise is? How should the testimony of experts be reported by the media? The chapters in the volume are organized into six sections: expertise and trust; situated and group expertise; expertise and public policy; expertise and virtue; expertise about value; and new directions. This volume will be of interest to scholars in such fields as philosophy, sociology, political theory, psychology, cognitive science, and bioethics. It will also be of relevance to policy-makers interested in the role that expertise plays in public policy.