If the thoughts of René-Jean Dupuy had to be reduced to an expression, it would be his method of ‘open dialectic’ applied to international law and society which enabled him to highlight the dynamic opposition of ‘relational’ and ‘institutional’ international trends in an impressive array of short surveys and ambitious synthesis. This article first aims to remind readers of the accuracy of Dupuy’s comprehensive approach to international law and society, in that he never disregarded the meaning of rules and institutions for actors – mainly political ones – the underlying values and justice considerations or even myths beyond technical rules or political antagonisms. But it does not suffice to celebrate the visionary and rhetorical skills of Dupuy. His contribution to the methodology of international law has to be assessed. Did he build up a new paradigm? Considering some incertainties in the method of open dialectic and some shortcomings in his core concepts (inter alia a quite static conception of sovereignty), it may be doubted.