A sophisticated account of the role that analogy may play in the identification and development of international law requires a jurisprudential understanding of legal reasoning. This chapter discusses the normative case for analogy, that is, the reasons why it is viewed as an authoritative type of argument in legal discourse, in particular its connection with the ideas of systematicity, the requirement that like cases be treated alike and the political ideal of the rule of law. It also examines two particularities of the international legal system that might be said to affect the value of analogies: the lack of centralised institutions that characterise domestic systems and the applicability of the so-called Lotus principle. Finally, it looks into the use of analogy as a technique for the codification and progressive development of international law.