As a terrific fan of conversation I think one of the best I have ever read took place on December 15, 1764, in Switzerland, between those two great men of letters, Boswell and Rousseau. It's true that we would expect their conversation to be lively, quarrelsome, thoughtful. Their lasting contribution to literature is immense; Boswell's London Journal and Rousseau's Confessions are classic works that have the rare, attractive value of remaining really good to read; in their hands, letter-writing was high art - in 1760, Rousseau wrote this note to Voitaire: In short, I hate you.

Superb. And it's also true that the timing of Boswell's visit to Rousseau was extremely fortunate. Two weeks after Boswell hoofed off, Voltaire had his revenge, in a pamphlet that accused Rousseau of abandoning his five children as nameless orphans, and killing his mother-in-law by his heartless treatment. He also mentioned in passing - falsely, I think - that Rousseau suffered from venereal disease. From the moment he read this attack (on December 31), we are told Rousseau was a broken man, either on the verge of madness or, lapsing into complete, raving insanity.

But when Boswell came to his door, Rousseau was at the height of his fame; in 1762, he published the main work of his political theory, Le Contrat Social, with its revolutionary beginning, Man is born free and everywhere he is in chains. Although drummed out of Paris, and then Geneva, he was nicely set up as an exile in Motiers, where he lived more or less as a recluse. His sole income was from writing, and there were no interruptions. Also, he could swan shamelessly around indoors dressed in a loose Armenian kaftan - the poor devil suffered from a constriction of the urethra, which caused frequent painful urination.

As for Boswell, he was 24, and in tremendously high spirits, up to his ears in lasciviousness and maliciousness, overjoyed at being made welcome by Rousseau. (But not overwhelmed. You have shown me great goodness, he told his host, but I have deserved it.) They dined in the kitchen. Boswell, a hypochondriac, would have felt quite at home when Rousseau told him, I need a chamber pot every minute. After scoffing soup, cabbage, turnip, carrots, cold pork, pickled trout, stoned pears, and chestnuts, with red and white wines, the two settled down to the serious task of talking a hell of a lot.

Rousseau was clearly charmed by Boswell's rampant ego and roguish manner. Boswell asked him, Do you think that I shall make a good barrister before a court of justice? His answer: Yes. But I regret that you have the talents necessary for defending a bad case.

They discussed literature, class and politics, religion, friendship, women, physiognomy - and cats. It's that particular subject of their interview that I especially adore. From Boswell on the Grand Tour, edited by the splendidly named Frederick A Pottle:

Rousseau: 'Do you like cats?'

Boswell: 'No.'

Rousseau: 'It is my test of character. There you have the despotic nature of men. They do not like cats because the cat is free and will never consent to becoming a slave. He will do nothing to your order, as the other animals do.'

Boswell: 'Nor a hen, either.'

Rousseau: 'A hen would obey your orders if you could make her understand them.'

Priceless.

Some people would like to see this intellectual tone, unpredictable content and level of retort used more often on h2g2.