The authors have earned fame for a hugely successful earlier book, Wittgenstein's Poker, in which a poker played a symbolical part in the dispute between Wittgenstein and Popper. Rousseau's dog Sultan plays no such part in this book about the antagonism that developed between Rousseau and Hume. Only on the penultimate page is there a single paragraph in which the authors comment on the unconditional love between man and dog that was the yardstick by which Rousseau judged all other friendships and to which none of his other friendships could live up. But the title might also have another explanation: two or three times in the text the authors have invented another "dog". The philosopher Grimm had written about the "companion who will not suffer him [Rousseau] to rest in peace", meaning the paranoid personality which he thought was Rousseau's alter ego. Grimm does not describe this alter ego as a dog, but the authors see it as one, doubtlessly having in mind that Winston Churchill had called his own depression his Black Dog.
When Rousseau was being driven from one place to another on the continent because of the authorities there objected to his writings, David Hume, then working at the British Embassy in Paris, had invited Rousseau to seek asylum in England, had brought him over in 1766, and intended to help him there in any way he could. Unfortunately Rousseau was by that time a florid paranoiac. Both in France and in England woundingly satirical but anonymous writings were circulating about him, and Rousseau suspected that the kindly Hume had had a hand in them and was plotting with his enemies against him. He wrote some bitter letters of accusation to Hume, and also denounced him in letters to his contacts on the continent, some of whom were also friends of Hume's, and this forced Hume into publishing his own defence.
The nature of the dispute between them was not of a philosophical kind at all (unlike, say, that of the dispute between Wittgenstein and Popper or that between Leibniz and Spinoza, so brilliantly examined by Matthew Stewart in his recent book The Courtier and the Heretic - see my review). Of course it COULD have been about philosophy: Rousseau was committed to the romantic and emotional approach, Hume to the ultra-rational examination of philosophical issues; Rousseau had come to hate the philosophes, Hume had greatly enjoyed their company while he was living in Paris. The dispute was not even overtly about their respective attitudes to society. Hume loved society and was at ease in it; Rousseau hated it and loved the solitary life. Such differences between them are handsomely set out in the excellent chapter 11, but if the two great thinkers were indeed "at war in the Age of Enlightenment" (the subtitle of the book), it is sadly not possible to dignify that war as one caused by differences in philosophy or life-style. Indeed, our authors do mention that in all the correspondence between Rousseau and Hume, "there is no dialogue or engagement about ideas", nor, to the best of my knowledge, did either of them take issue in print directly with the philosophical ideas of the other. Their war took the form exclusively of an attack by a floridly paranoiac Rousseau on his benefactor, and then, because the paranoiac was at that time so famous, of Hume feeling forced (against the initial advice of his friends) into defending himself against the charges circulating against him in Europe, and doing so in an uncharacteristically intemperate and less than entirely honest manner.
The story of the actual quarrel (which begins only half-way through the book) is well told. The authors give a judicious account of and carefully expose the inconsistencies in the cases of both contenders in this sad and pathetic story. Rousseau was a very sick man, but Hume, too, comes out it all rather worse than is perhaps commonly assumed, especially in the summing up in the last chapter.
In the end it was not any clash of ideas but merely gossip that excited the intellectuals of Europe about this dispute. It was a great "media story", but not a significant one. And like so many media stories today, it was about personalities and not about issues. Although there are some good assessments of Rousseau's and Hume's importance in the history of Europe, the book focusses on what was least important, least stimulating, least edifying and least enduring about them. It is the authors' good right to give their book this focus. And it is a good read.