He agreed with Shaftesbury as to the natural goodness of man; he agreed with Mandeville that innocence of manners is incompatible with the conditions of a civilised society.

He was an optimist in regard to human nature, a pessimist in regard to civilisation.
In his first Discourse he begins by appreciating the specious splendour of modern enlightenment, the voyages of man's intellect among the stars, and then goes on to assever that in the first place men have lost, through their civilisation, the original liberty for which they were born, and that arts and science, flinging garlands of flowers on the iron chains which bind them, make them love their slavery; and secondly that there is a real depravity beneath the fair semblance and "our souls are corrupted as our sciences and arts advance to perfection." Nor is this only a modern phenomenon; "the evils due to our vain curiosity are as old as the world." For it is a law of history that morals fall and rise in correspondence with the progress and decline of the arts and sciences as regularly as the tides answer to the phases of the moon.
This "law" is exemplified by the fortunes of Greece, Rome, and China, to whose civilisations the author opposes the comparative happiness of the ignorant Persians, Scythians, and ancient Germans.

"Luxury, dissoluteness, and slavery have been always the chastisement of the ambitious efforts we have made to emerge from the happy ignorance in which the Eternal Wisdom had placed us." There is the theological doctrine of the tree of Eden in a new shape.
Rousseau's attempt to show that the cultivation of science produces specific moral evils is feeble, and has little ingenuity; it is a declamation rather than an argument; and in the end he makes concessions which undo the effect of his impeachment.

The essay did not establish even a plausible case, but it was paradoxical and suggestive, and attracted more attention than Turgot's thoughtful discourse in the Sorbonne.

D'Alembert deemed it worthy of a courteous expression of dissent; [Footnote: In the Disc.Prel.to the Encyclopaedia.] and Voltaire satirised it in his Timon.
2.
In the Discourse on Inequality Rousseau dealt more directly with the effect of civilisation on happiness.