But though his religion had more articles, he was as determined a foe of “superstition” as Voltaire, Diderot, and the rest.  He did not go so far as they in aggressive rationalism—­he belonged to an older generation—­but his principles were the same.

The Abbe de Saint-Pierre thus represents the transition from the earlier Cartesianism, which was occupied with purely intellectual problems, to the later thought of the eighteenth century, which concentrated itself on social problems.  He anticipated the “humanistic” spirit of the Encyclopaedists, who were to make man, in a new sense, the centre of the world.  He originated, or at least was the first to proclaim, the new creed of man’s destinies, indefinite social progress.

CHAPTER VII

NEW CONCEPTIONS OF HISTORY:  MONTESQUIEU, VOLTAIRE, TURGOT

The theory of human Progress could not be durably established by abstract arguments, or on the slender foundations laid by the Abbe de Saint-Pierre.  It must ultimately be judged by the evidence afforded by history, and it is not accidental that, contemporaneously with the advent of this idea, the study of history underwent a revolution.  If Progress was to be more than the sanguine dream of an optimist it must be shown that man’s career on earth had not been a chapter of accidents which might lead anywhere or nowhere, but is subject to discoverable laws which have determined its general route, and will secure his arrival at the desirable place.  Hitherto a certain order and unity had been found in history by the Christian theory of providential design and final causes.  New principles of order and unity were needed to replace the principles which rationalism had discredited.  Just as the advance of science depended on the postulate that physical phenomena are subject to invariable laws, so if any conclusions were to be drawn from history some similar postulate as to social phenomena was required.

It was thus in harmony with the general movement of thought that about the middle of the eighteenth century new lines of investigation were opened leading to sociology, the history of civilisation, and the philosophy of history.  Montesquieu’s De l’esprit des lois, which may claim to be the parent work of modern social science, Voltaire’s Essai sur les moeurs, and Turgot’s plan of a Histoire universelle begin a new era in man’s vision of the past.

1.

Montesquieu was not among the apostles of the idea of Progress.  It never secured any hold upon his mind.  But he had grown up in the same intellectual climate in which that idea was produced; he had been nurtured both on the dissolving, dialectic of Bayle, and on the Cartesian enunciation of natural law.  And his work contributed to the service, not of the doctrine of the past, but of the doctrine of the future.

For he attempted to extend the Cartesian theory to social facts.  He laid down that political, like physical, phenomena are subject to general laws.  He had already conceived this, his most striking and important idea, when he wrote the Considerations on the Greatness and Decadence of the Romans (1734), in which he attempted to apply it: