The figure of the “arbiter of Europe” represented an aporia as far back as the early modern era, since it combined the ideal of hegemony with the political ideal of wise and disinterested judgement. The appearance of a “European public reason,” for lack of a genuine public opinion, necessitated a growing development of the latter. Although we can discern a great variety of political practices of arbitration, the seventeenth and eighteenth centuries showed a growing need for legal definitions, which the flaws of the nineteenth century’s Concert of Europe only served to reinforce. Hence, in modern times the figure of the arbiter positioned itself in relation to two poles: on the one hand was the arbiter embodied in a power, which enjoyed the advantages and prestige of this honorific and often self-proclaimed title; and on the other was an arbiter using influence to guide negotiations in respect of the new international law of arbitration. Attempts to reconcile the two poles clearly show the political difficulty of this notion of arbiter, which cannot be fully resolved solely within the domain of law.