This monograph discusses the question of what it is to be a reason – mainly in practical ethics – and proposes an original contribution to metaethics.It critically examines theories of metaethical realism, constructivism and error theory and identifies several misunderstandings or unclarities in contemporary debates. Based on this examination, the book suggests a distinction between a conceptual question, that can be answered by pure first-personal thinking, and a material question, that targets responses to reasons as a natural phenomenon in space (...) and time and that can be answered by help of the sciences. While this book defends a sharp distinction between these approaches, it also argues that the insights gained by the distinct approaches can be fruitfully integrated into a comprehensive picture.The comprehensive picture promoted in this book, based on both philosophical analysis and resources from psychology and cognitive science, is a picture of reasons as items in a collective archive of mind – reconfiguring the “domain of reasons” as a collectively established and socially cultivated fund of considerations with normative weight. The developed Collective Archive View combines Reasons Fundamentalism as an answer to the conceptual question, with a social ontological proposal, similar to Haslanger’s critical realism, as an answer to the material question.Thereby, it introduces central ideas from the field of social metaphysics into metaethics. At the same time, it offers a way of settling some controversies within metaethics, going on between proponents of Reasons Fundamentalism and Constitutivism, realism and constructivism, as well as proponents of mind-dependence and mind-independence of normative facts. Finally, the proposal enables us to envision and conceptualize genuine normative change within a metaethical theory. (shrink)