Trust is an authoritative collection of previously published articles and is unique in the growing literature on trustworthiness. The broad ranging articles are organized into three parts, expressing three definite answers to the question posed in the introduction: Why does trustworthiness pay? Part I, 'Trust as Strategy', stipulates that trust is an investment in reputation. Part II, 'Trust as Taste', argues that agents have a preference for trustworthiness, which may explain the anomaly of trustworthiness in single-shot games. Part III, 'Trust as Trait', maintains that trust is a trait that evolutionary selection may favor. In his extensive introductory essay, Elias Khalil elaborates and contrasts the strengths and weaknesses of each answer.Including over 35 articles from diverse disciplines such as economics, sociology, political science, anthropology, philosophy, psychology, evolutionary biology, and organizational studies, Trust will be a valuable reference for many years to come.