The first part of this work analyses the universalist and the particularist conceptions of reasons. The second part projects this analysis to the legal domain. The author stresses that universalism and particularism regarding reasons are mutually exclusive theories linked to incompatible conceptions of norms, i.e. norms as strict universal conditionals and norms as defeasible conditionals. In giving an account of this tenet, different meanings of universality and defeasibility are explored. A parallel debate regarding reasons can be found in the legal domain, where two contrasting categories of norms are usually distinguished: rules and principles. On this issue the author argues that the conception of legal reasons depends on the way in which this contrast between different kinds of legal norms is shaped.