ABSTRACT
This chapter aims to identify factors which contribute to the formation of unwritten international law as a normative system. It analyzes some of the dominant strands of legal theory that have evolved over the course of the 20th century, and assess their aptitude to advance the understanding of the concept of unwritten international law and to improve the methodology for its ascertainment. To Aristotle, the specific value of these unwritten laws stems from the fact that they emerge from a slow, fragmentary process, through the practice of the community, whose totality is able to develop smarter answers to its needs than the wisest individual ruler could. Unwritten international law, which arises by way of self-organisation of the international community, whether of its totality or of parts of it, contributes significantly to the promotion of order and stability in international relations; yet it aggregates without formal enactment and without centralised rationalistic design.
