Zaretsky, Robert, and John T. Scott. The Philosophers' Quarrel: Rousseau, Hume, and the Limits of Human Understanding. New Haven: Yale UP, 2009.
They made a very odd couple. The French philosopher (or rather, Swiss - he was born in Geneva) was a small, gesticulating man with animated features and a bizarre taste in clothes: wearing what he called an Armenian caftan, he sought (like Lawrence of Arabia in the Beyond the Fringe sketch) to pass unnoticed in the street. Hume was a large, portly figure with an amiable but bovine face and a strangely vacant stare. He dressed conventionally; indeed, convention was something in which he - unlike Rousseau - rather strongly believed. The intellectual differences went deeper than that. Rousseau idealised natural innocence and saw the socialisation of mankind as a process of corruption. Modern man was an alienated being, and radical changes were needed to remedy that. For Hume, the civilising process in human history involved a complex web of interactions, through which moral behaviour was learned and refined, and political institutions were settled and gradually improved. Yet these two very contrasting thinkers did have some common ground. While both were products of the "Age of Reason", neither believed that reason, as such, had any motive power: sentiment and sympathy were the generating forces of human behaviour. Both, too, had suffered from the disapproval of the ecclesiastical authorities (Calvinism being the doctrinal bedrock of Edinburgh as well as Geneva). On religious issues, indeed, Hume was the more radical of the two. While Rousseau preached his own portentous brand of "natural religion", Hume demolished all theological arguments, including "natural" ones. With such very different temperaments, and largely different beliefs, it is a miracle that the warm friendship between them lasted as long as it did - which is to say, six months on Hume's side and about three on Rousseau's. . . .
Read the rest here: http://www.standpointmag.co.uk/node/1158/full.