The world had begun to abandon the theory of corruption, degeneration, and decay.
Some years later the optimistic theory of the perfection of the universe found an abler exponent in Leibnitz, whom Diderot calls the father of optimism. [Footnote: See particularly Monadologie, ad fin. published posthumously in German 1720, in Latin 1728; Theodicee, Section 341 (1710); and the paper, De rerum originatione radicali, written in 1697, but not published till 1840 (Opera philosophica, ed. Erdmann, p. 147 sqq).] The Creator, before He acted, had considered all possible worlds, and had chosen the best. He might have chosen one in which humanity would have been better and happier, but that would not have been the best possible, for He had to consider the interests of the whole universe, of which the earth with humanity is only an insignificant part. The evils and imperfections of our small world are negligible in comparison with the happiness and perfection of the whole cosmos. Leibnitz, whose theory is deduced from the abstract proposition that the Creator is perfect, does not say that now or at any given moment the universe is as perfect as it could be; its merit lies in its potentialities; it will develop towards perfection throughout infinite time.
The optimism of Leibnitz therefore concerns the universe as a whole, not the earth, and would obviously be quite consistent with a pessimistic view of the destinies of humanity. He does indeed believe that it would be impossible to improve the universal order, “not only for the whole, but for ourselves in particular,” and incidentally he notes the possibility that “in the course of time the human race may reach a greater perfection than we can imagine at present.” But the significance of his speculation and that of Malebranche lies in the fact that the old theories of degeneration are definitely abandoned.
THE DOCTRINE OF DEGENERATION: THE ANCIENTS AND MODERNS