evening and with hospitable intent, a host offers his daughters and wife to his guests, where the son espouses his mother out of politeness, where the union of the sexes is a religious festivity celebrated in public. —­ And, pushing things to extremes, the logician ends with five or six pages calculated “to make one’s hair stand on end,"[19] himself avowing that his doctrine is “neither suited for children nor for adults.” —­With Diderot, to say the least, these paradoxes have their correctives.  In his pictures of modern ways and habits, he is the moralist.  He not only is familiar with all the chords of the human keyboard, but he classifies each according to its rank.  He loves fine and pure tones, and is full of enthusiasm for noble harmonies; his heart is equal to his genius.[20] And better still, on the question of primitive impulses arising, he assigns, side by side with vanity, an independent and superior position to pity, friendship, kindness and charity; to every generous affection of the heart displaying sacrifice and devotion without calculation or personal benefit. —­ But associated with him are others, cold and narrow, who form moral systems according to the mathematical methods of the ideologists, [21] after the style of Hobbes.  One motive alone satisfies these, the simplest and most palpable, utterly gross, almost mechanical, completely physiological, the natural animal tendency of avoiding pain and seeking pleasure: 

“Pain and pleasure,” says Helvétius, “form the only springs of the moral universe, while the sentiment of vanity is the only basis on which we can lay the foundations of moral usefulness.  What motive but that of self-interest could lead a man to perform a generous action?  He can as little love good for the sake of good as evil for the sake of evil."[22] “The principles of natural law, say the disciples, are reduced to one unique and fundamental principle, self-preservation."[23] “To preserve oneself, to be happy,” is instinct, right and duty.  “Oh, yea,"[24] says nature, “who, through the impulsion I bestow on you, tending towards happiness at every moment of your being, resist not my sovereign law, strive for your own felicity, enjoy fearlessly and be happy!” But to be happy, contribute to the happiness of others; if you wish them to be useful to you, be useful to them. “every man, from birth to death, has need of mankind.”  “Live then for them, that they may live for you.”  “Be good, because goodness links hearts together; be gentle, because gentleness wins affection; be modest, because pride repels beings full of their self-importance. . . .  Be citizens, because your country is necessary to ensure your safety and well-being.  Defend your country, because it renders you happy and contains your possessions.”

Virtue thus is simply egotism furnished with a telescope; man has no other reason for doing good but the fear of doing himself harm, while self-devotion consists of self-interest.