But the terrible wars of this period exhausted Europe, and this financial exhaustion has supplied the requisite conditions for attaining a measure of felicity never realised in the past.
Peace is an advantageous condition for the progress of reason, but especially when it is the result of the exhaustion of peoples and their satiety of fighting.

Frivolous ideas disappear; political bodies, like organisms, have the care of self-preservation impressed upon them by pain; the human mind, hitherto exercised on agreeable objects, falls back with more energy on useful objects; a more successful appeal can be made to the rights of humanity; and princes, who have become creditors and debtors of their subjects, permit them to be happy in order that they may be more solvent or more patient.
This is not very lucid or convincing; but the main point is that intellectual enlightenment would be ineffective without the co-operation of political events, and no political events would permanently help humanity without the progress of knowledge.
Public felicity consists--Chastellux follows the Economists--in external and domestic peace, abundance and liberty, the liberty of tranquil enjoyment of one's own; and ordinary signs of it are flourishing agriculture, large populations, and the growth of trade and industry.
He is at pains to show the superiority of modern to ancient agriculture, and he avails himself of the researches of Hume to prove the comparatively greater populousness of modern European countries.

As for the prospect of peace, he takes a curiously optimistic view.

A system of alliances has made Europe a sort of confederated republic, and the balance of power has rendered the design of a universal monarchy, such as that which Louis XIV.

essayed, a chimera.