100.
Rousseau; the rule founded on sentiment; Nature as the source of justice; man perfects himself in proportion as he approaches Nature (according to Voltaire, in proportion as he leaves Nature behind). The very same periods seem to the one to demonstrate the progress of humanity and, to the other, the increase of injustice and inequality.
Voltaire, who still understood umanità in the sense of the Renaissance, as also virtù (as "higher culture"), fights for the cause of the "honnêtes gens" "la bonne compagnie" taste, science, arts, and even for the cause of progress and civilisation.
The flare-up occurred towards 1760: On the one hand the citizen of Geneva, on the other le seigneur de Ferney. It is only from that moment and henceforward that Voltaire was the man of his age, the philosopher, the representative of Toleration and of Disbelief (theretofore he had been merely un bel esprit). His envy and hatred of Rousseau's success forced him upwards.
"Pour 'la canaille' un dieu rémunérateur et vengeur"—Voltaire.
The criticism of both standpoints in regard to the value of civilisation. To Voltaire nothing seems finer than the social invention: there is no higher goal than to uphold and perfect it. L'honnêteté consists precisely in respecting social usage; virtue in a certain obedience towards various necessary "prejudices" which favour the maintenance of society. Missionary of Culture, aristocrat, representative of the triumphant and ruling classes and their values. But Rousseau remained a plebeian, even as hommes de lettres, this was preposterous; his shameless contempt for everything that was not himself.
The morbid feature in Rousseau is the one which happens to have been most admired and imitated. (Lord Byron resembled him somewhat, he too screwed himself up to sublime attitudes and to revengeful rage—a sign of vulgarity; later on, when Venice restored his equilibrium, he understood what alleviates most and does the most good ... l'insouciance.)
In spite of his antecedents, Rousseau is proud of himself; but he is incensed if he is reminded of his origin....
In Rousseau there was undoubtedly some brain trouble; in Voltaire—rare health and lightsomeness. The revengefulness of the sick; his periods of insanity as also those of his contempt of man, and of his mistrust.
Rousseau's defence of Providence (against Voltaire's Pessimism): he had need of God in order to be able to curse society and civilisation; everything must be good per se, because God had created it; man alone has corrupted man. The "good man" as a man of Nature was pure fantasy; but with the dogma of God's authorship he became something probable and even not devoid of foundation.