Diplomacy, in the proper and unhurried sense of the word, is the conduct of relations between sovereign polities by means other than violence — and, more importantly, the cultivated manners by which such conduct is made legible to history. It is at once a craft (the drafting of instruments), a theatre (the audience, the toast, the silence at the right moment), and an archive (the dispatches that follow).
The 1815 Vienna Regulation arranged ambassadors into four classes; the 1961 Convention rearranged them into three. Between those two dates, a continent learned, lost, and re-learned the art of speaking to a peer without raising one's voice. The encyclopaedist must therefore treat diplomacy not as a department of foreign policy, but as a genre: it has its own forms, its own decorum, its own permitted ornaments, and — though one is loath to admit it — its own well-bred clichés.
This entry proceeds, accordingly, from the lexical to the ceremonial. First we settle the word; then we describe the offices, the ranks, the credentials. The architecture of the second Article will be ceremony itself. Patience, reader, is part of the method.