Treaty interpretation is a matter of legal methodology, a comprehensive notion embracing a great variety of subjects. In the Diagram published together with this study, the present writer gives his own view of legal methodology as applied to international law. The “legal process” as shown therein is a complicated one, certain parts of which have been examined in earlier studies, viz., the principles of rational organization, the recognized manifestations of international law, and the existence of a hierarchy among them. Treaty interpretation as dealt with, here, belongs to the wide category of problems designated in the Diagram as those of the ascertainment of the content (meaning, message) of the recognized manifestations of international law. For reasons/which, it is hoped, will become clear in the following pages, it is important to place treaty interpretation and the whole of ascertainment of content in the context of methodology generally, not isolated from the other questions involved in the application of recognized manifestations or from the problems surrounding the latter, such as the doctrine of “sources”. As to the link between the present subject and that of the ascertainment of the content of recognized manifestations other than treaties, it is readily agreed that doctrinal treatment of the former would gain by a contrasting sketch of the latter, but since the present study already exceeds the limits of the habitual article, this writer has to forego what otherwise would be a legitimate pursuit.