In 1745, when Voltaire was briefly in the favor of
Louis XV, he first met the younger J.J. Rousseau, native of
In 1755 Rousseau had written a Prize Essay for the
August 30, 1755, from Les DELICES. (Voltaire’s home outside
I have received, sir, your new book against the human race, and I thank you for it. You will please people by your manner of telling them the truth about themselves, but you will not alter them. The horrors of that human society--from which in our feebleness and ignorance we expect so many consolations--have never been painted in more striking colors: no one has ever been so witty as you are in trying to turn us into brutes: to read your book makes one long to go about all fours. Since, however, it is now some sixty years since I gave up the practice, I feel that it is unfortunately impossible for me to resume it: I leave this natural habit to those more fit for it than are you and I. Nor can I set sail to discover the aborigines of Canada, in the first place because my ill-health ties me to the side of the greatest doctor  in Europe, and I should not find the same professional assistance among the Missouris: and secondly because war is going on in that country, and the example of the civilized nations has made the barbarians almost as wicked as we are ourselves. I must confine myself to being a peaceful savage in the retreat I have chosen--close to your country, where you yourself should be.
I agree with you that science and literature have sometimes done a great deal of harm. Tasso's  enemies made his life a long series of misfortunes: Galileo's enemies kept him languishing in prison, at seventy years of age, for the crime of understanding the revolution of the earth: and, what is still more shameful, obliged him to forswear his discovery. Since your friends began the Encyclopedia, their rivals attack them as deists, atheists--even Jansenists.
If I might venture to include myself among those whose works have brought them persecution as their sole recompense, I could tell you of men set on ruining me from the day I produced my tragedy Oedipus… I have no right to complain: Alexander Pope, Descartes, Bayle --a hundred others--have been subjected to the same, or greater, injustice: and my destiny is that of nearly everyone who has loved letters too well.
Confess, sir, that all these things are, after all, but little personal pin-pricks, which society scarcely notices. What matter to humankind that a few drones steal the honey of a few bees? Literary men make a great fuss of their petty quarrels: the rest of the world ignores them, or laughs at them.
They are, perhaps, the least serious of all the
ills attendant on human life. …Confess that
If anyone has a right to complain of letters, I am that person, for in all times and in all places they have led to my being persecuted: still, we must needs love them in spite of the way they are abused--as we cling to society, though the wicked spoil its pleasantness: as we must love our country, though it treats us unjustly: and as we must love and serve the Supreme Being, despite the superstition and fanaticism which too often dishonor His service.
M. Chappus tells me your health  is very unsatisfactory: you must come and recover here in your native place, enjoy its freedom, drink (with me) the milk of its cows, and browse on its grass. I am yours most philosophically and with sincere esteem.
Adapted from http://www.whitman.edu/VSA/letters/8.30.1755.html
 Dr. Theodore Tronchin, who was Voltaire's doctor from 1754 until Voltaire's death, was a member of a distinguished Genevan family and one of the earliest advocates of the value of fresh air, soberness, temperance, and chastity in promoting health.
 Torquato Tasso, a famous Italian court poet of the 16th century, writer of the poem Gerusalemme Liberata, an epic verse account of the Crusades.
 Jansenism was an ultra pious movement within French
Catholicism; puritanical and devout, determined to live saintly lives in
society, they can be seen as a type of Catholic Puritans. They were ultimately condemned both by the
French kings and by
 Rousseau suffered throughout his life from a painful condition of the urinary tract, and wrote in excruciating detail about his attempts at cures in his posthumously published Confessions.