We may perhaps best conceive all that this change meant by supposing what a difference it would make to us if it were suddenly discovered that the old system which Copernicus upset was true after all, and that we had to think ourselves back into a strictly limited universe of which the earth is the centre.  The loss of its privileged position by our own planet; its degradation, from a cosmic point of view, to insignificance; the necessity of admitting the probability that there may be many other inhabited worlds—­all this had consequences ranging beyond the field of astronomy.  It was as if a man who dreamed that he was living in Paris or London should awake to discover that he was really in an obscure island in the Pacific Ocean, and that the Pacific Ocean was immeasurably vaster than he had imagined.  The Marquise, in the Plurality of Worlds, reacts to the startling illumination:  “Voila l’univers si grand que je m’y perds, je ne sais plus ou je suis; je ne suis plus rien.—­La terre est si effroyablement petite!”

Such a revolution in cosmic values could not fail to exert a penetrating influence on human thought.  The privileged position of the earth had been a capital feature of the whole doctrine, as to the universe and man’s destinies, which had been taught by the Church, and it had made that doctrine more specious than it might otherwise have seemed.  Though the Churches could reform their teaching to meet the new situation, the fact remained that the Christian scheme sounded less plausible when the central importance of the human race was shown to be an illusion.  Would man, stripped of his cosmic pretensions, and finding himself lost in the immensities of space, invent a more modest theory of his destinies confined to his own little earth—­si effroyablement petite?  The eighteenth century answered this question by the theory of Progress.

10.

Fontenelle is one of the most representative thinkers of that period—­we have no distinguishing name for it—­which lies between the characteristic thinkers of the seventeenth century and the characteristic thinkers of the eighteenth.  It is a period of over sixty years, beginning about 1680, for though Montesquieu and Voltaire were writing long before 1740, the great influential works of the “age of illumination” begin with the Esprit des lois in 1748.  The intellectual task of this intervening period was to turn to account the ideas provided by the philosophy of Descartes, and use them as solvents of the ideas handed down from the Middle Ages.  We might almost call it the Cartesian period for, though Descartes was dead, it was in these years that Cartesianism performed its task and transformed human thought.