by Cardlinger » 17 Feb 2017, 21:17
Zosimus has nailed the big ones in rhetoric and self-interest.
In terms of the main branches of philosophy, the obvious few are
Ethics (especially of actions and motivation)
Logic (in conveying of orders and actions)
Political Philosophy (in interaction)
Less so Metaphysics, Epistemology and Aesthetics, but I suppose you could argue these fit within Diplomacy too. Then you can get right down into philosophy of the mind, of language, of education, of history...
If you can convince an opponent of Stoicism (our own suffering is caused by an error on one's own judgement) you may go some way to getting them to go along with you! Also, if you're not just going Classics then Sun Tzu as a philosophical text and its relations to diplomacy are obvious.
Best,
Cardlinger