A focus on reasons for action and practical reason is the perspective chosen by many contemporary legal philosophers for the analysis of some central questions of their discipline. This book offers a critical evaluation of that approach, by carefully examining the empirical, logical and normative problems hidden behind the concepts of `reason for action' and `practical reasoning'. Unlike most other works in this field, it is a meta-theoretical study which analyses and compares how different theories use the notion of reason in their reconstruction of problems concerning issues such as normativity, the acceptance of norms, or the justification of judicial decisions. This book is directed primarily to scholars specializing in legal theory and concerned with the contribution practical philosophy can make to it, but it also contains important arguments and insights for all those interested in the controversy between legal positivists and their critics, in the theory of human action or in reason-based practical theories in general.