Spheres of Reason comprises nine original essays on the philosophy of normativity, written by a combination of internationally renowned and up-and-coming philosophers working at the forefront of the topic. On one broad construal the normative sphere concerns norms, requirements, oughts, reasons, reasoning, rationality, justification, value. These notions play a central role in both everyday thought and philosophical enquiry; but there remains considerable disagreement about how to understand normativity -- its nature, metaphysical and epistemological bases -- and how different aspects of normative thought connect to one another. As well as exploring traditional and ongoing issues central to our understanding of normativity -- especially those concerning reasons, reasoning and rationality -- the volume's essays develop new approaches to and perspectives in the field. Notably, they make a timely and distinctive contribution to normativity as it features across each of the practical, epistemic and affective regions of thought, including the important issue of how normativity as it applies to action, belief and feeling may (or may not) be connected. In doing so, the essays engage topics within the philosophy of mind and action, epistemology, normative ethics and metaethics. With an editor's introduction providing a comprehensive and accessible background to the subject, Spheres of Reason is essential reading to anyone interested in the nature of normativity and the bearing it has on human thought.