The first of these conditions was a firm disregard of authority; the second was an abstention from the premature concoction of system.  The reign of ignorance and prejudice was made inveterate by deference to tradition:  the reign of truth was hindered by the artificial boundary-marks set mischievously deep by the authors of systems.  As the whole spirit of theology is both essentially authoritative and essentially systematic, this disparagement was full of tolerably direct significance.  It told in another way.  The Sorbonne, the universities, the doctors, had identified orthodoxy with Cartesianism.  “It is hard to believe,” says D’Alembert in 1750, “that it is only within the last thirty years that people have even begun to renounce Cartesianism.”  He might have added that one of the most powerful of his contemporaries, Montesquieu himself, remained a rigid Cartesian to the end of his days.  “Our nation,” he says, “singularly eager as it is for novelties in all matters of taste, is in matters of science extremely attached to old opinions.”  This remark remains true of France to the present hour, and it would be an interesting digression, did time allow, to consider its significance.  France can at all events count one master innovator, the founder of Cartesianism himself.  D’Alembert points out that the disciples violate the first maxims of their chief.  He describes the hypothesis of vortices and the doctrine of innate ideas as no longer tenable, and even as ridiculous; but do not let us forget, he says with a fine movement of candour, that it was Descartes who opened the way; he who set an example to men of intelligence, of shaking off the yoke of scholasticism, of opinion, of authority—­in a word, of prejudices and barbarism.  Those who remain faithful to his hypothetical system, while they abandon his method, may be the last of his partisans, but they would assuredly never have been the first of his disciples.

By system the Encyclopaedists meant more or less coherent bodies of frivolous conjecture.  The true merit of the philosopher or the physicist is described as being to have the spirit of system, yet never to construct a system.  The notion expressed in this sentence promises a union of the advantages of an organic synthesis, with the advantages of an open mind and unfettered inquiry.  It would be ridiculous to think, says D’Alembert, that there is nothing more to discover in anatomy, because anatomists devote themselves to researches that may seem to be of no use, and yet often prove to be full of use in their consequences.  Nor would it be less absurd to lay a ban on erudition, on the pretext that our learned men often give themselves up to matters of trivial import.