All his activities were urged by the dream of a humanity regenerated by reason, all his energy devoted to bringing about its accomplishment.

Saint-Pierre's idea of perpetual peace inspired an early essay on the scourge of war.
The theories of Rousseau exercised at first an irresistible attraction, but modern civilisation had too strong a hold on him; he was too Parisian in temper to acquiesce for long in the doctrine of Arcadianism.
He composed a book on The Savage to illustrate the text that the true standard of morality is the heart of primitive man, and to prove that the best thing we could do is to return to the forest; but in the process of writing it he seems to have come to the conclusion that the whole doctrine was fallacious.

[Footnote: Mercier's early essay: Des malheurs de la guerre et des avantages de la paix (1766).

On the savage: L'homme sauvage (1767).

For the opposite thesis see the Songes philosophiques (1768).