Nevertheless, the Théodicée became the most widely read of Leibniz’ books, and succeeding generations knew him as “the best-of-all-possible-worlds man.” If we must regret the edifying absurdity of that performance, our respect for the author revives when we contemplate the prodigious variety of his intellectual interests. Though science was but one corner of his thought, he was fascinated by it; if he had to live another life, he told Bayle, he would have been a biologist. 75 He was one of the profoundest mathematicians of an age rich in mathematicians. He bettered Descartes’ formula for measuring force.* His conception of matter as energy seemed to his time a bravura of metaphysics, but it is now a commonplace of physics. He described matter as our confused perception of the operations of force. Like our contemporary theorists he rejected the “absolute motion” assumed by Newton; motion, said Leibniz, “is simply change in the relative position of bodies, and thus is nothing absolute, but consists in a relation.” 76 Anticipating Kant, he interpreted space and time not as objective realities but as perceptual relations: space as perceived coexistence, time as perceived succession—views adopted in relativity theories today. In his final year (1715) Leibniz entered into a long correspondence with Samuel Clarke about gravitation; this seemed to him another occult quality, acting at enormous distances through an apparent void; it would be, he objected, a perpetual miracle; no greater, replied Clarke, than “preestablished harmony.” 77 Leibniz feared that Newton’s theory of the cosmic mechanism would make many atheists; on the contrary, said Clarke, the majestic order revealed by Newton would strengthen the belief in God; 78 the aftermath justified Leibniz.
In biology Leibniz vaguely visioned evolution. Like many thinkers before and after him he saw a “law of continuity” running through the organic world; but he extended the concept to the supposedly inorganic world as well. Everything is a point or stage in an endless series, and is connected with everything else through an infinite number of intermediate forms; 79 there is, so to speak, an infinitesimal calculus running through reality.
Nothing is accomplished all at once, and it is one of my great maxims . . . that nature makes no leaps. . . . This law of continuity declares that we pass from the small to the great—and the reverse—through the medium, in degree as well as in parts. 80 [This is now questioned by many physicists.] . . . Men are linked with animals, these with plants, and these again with fossils, which in their turn are connected with those bodies which sense and imagination represent to us as completely dead and inorganic. 81
In this majestic continuity all antitheses dissolve through a great chain of being and hardly perceptible differences, from the simplest matter to the most complex, from the lowliest animalcule to the greatest ruler, genius, or saint.
Leibniz’ mind seemed to span the whole continuity that he described. He was au courant with every science; he knew the history of nations and of philosophy; he touched the worldly affairs of a dozen states; he was at home with atoms and with God. In 1693 he published a paper on the beginnings of the earth, quietly ignoring Genesis, and he developed his geological ideas in a treatise, Protogaea, which was published (1749) after his death. Our planet, he thought, had once been an incandescent globe; it gradually cooled, contracted, and formed a crust; as it cooled, the vapor surrounding it condensed into water and oceans—which became salty by dissolving minerals in the crust. Subsequent geological changes were due either to the action of water flooding the surface, leaving sedimentary formations, or to the explosion of subterranean gases, leaving igneous rocks. The same treatise gave an excellent explanation of fossils, 82 and advanced toward a theory of evolution. It seemed to him “worthy of belief that in the course of vast changes” in the crust of the earth “even the species of animals have many times been transformed.” 83 He thought it probable that the earliest animals were marine forms, and that the amphibia and land animals were descended from these. 84 Like some optimists of the nineteenth century, he saw in this evolutionary transformism one basis for faith in “a perpetual and unrestricted progress of the universe. . . . Progress will never come to an end.” 85
From biology Leibniz jumped to Roman law, and from this to Chinese philosophy. His Novissima Sinaica (1697)—“the latest news from China”—eagerly took up the reports that missionaries and merchants were sending from the “Middle Kingdom.” He held it probable that in philosophy, mathematics, and medicine the Chinese had made discoveries which might be of great help to Western civilization, and he urged cultural links with Russia partly as a means of opening cultural communication with the East. He corresponded with scholars, scientists, and statesmen in twenty countries and three languages. He wrote some three hundred letters every year; fifteen thousand of them have been preserved; 86 Voltaire’s correspondence rivals this in quantity, but yields to it in intellectual diversity. Leibniz suggested an international culture bourse, or exchange, through which men of learning could compare notes and ideas. 87 He planned an international language—“characteristica universalis”—in which each idea in philosophy and science would have its symbol or character, so that thinkers could manipulate notions by this ars combinatoria, just as mathematicians used signs for quantities; so he came close to founding mathematical or symbolic logic. 88 By a kind of noble futility he distributed himself into so many areas that he left hardly anything but fragments behind him.
Our eager polymath found no time for marriage. At last, aged fifty, he proposed; but, says Fontenelle, “the lady asked for time to take the matter into consideration, and as Leibniz thus obtained leisure to consider the matter again, he never married.” 89 After his travels, and his flights into diplomacy, he treasured the privacy of his study, and he who had touched half the world with the tentacles of his mind now kept his friends at a distance as enemies to his work. He lost himself in reading and writing, often through the night, seldom taking note of Sundays or holidays. He had no servant; he sent out for his meal, and ate it alone in his room. 90 If he stirred out it was to make researches, or pursue his schemes for the advancement of learning, science, or amity.
He dreamed of establishing academies in the great capitals, and succeeded in one. The Berlin Academy was founded (1700) on his initiative, and elected him its first president. He met Peter the Great at Torgau (1712), and again at Carlsbad and Pyrmont; he proposed a similar academy for St. Petersburg; the Czar loaded him with gifts, and adopted his suggestion for governing Russia through administrative “colleges”; but Leibniz did not live to see the Academy of St. Petersburg take form in 1724. In 1712 we find him in Vienna, itching for an Imperial post and pregnant with another academy; he submitted to Charles VI a plan for an institution that would promote not only science but education, agriculture, and industry; and he offered his services to direct it. The Emperor raised him to the ranks of the nobility, and made him an Imperial councilor (1712).
His long absences from Hanover angered the new Elector George; Leibniz’ salary was for a period discontinued, and he was warned that it was time, after a quarter century of interruptions, that he should finish his history of the house of Brunswick. When Queen Anne died, George left Hanover to take the throne of England. Three days after this departure Leibniz arrived from Vienna (1714). He had hoped to be taken to London and enjoy there some loftier office and emoluments; he sent conciliatory letters to the new King; but George I answered that until the Annals were complete Leibniz had better remain in Hanover. 91 Besides, England had not forgiven him for disputing with Newton the parentage of calculus.
Disappointed and lonely, he struggled for two years more to believe in the good intentions of the universe. The man who was remembered in the eighteenth century as the apostle of optimism died in pain of gout and stone at Hanover on November 14, 1716. His death was not noticed by the Berlin Academy, nor by the German courtiers in London, nor by any friends at home, for these had been alienated by his absences and his privacy. No clergyman came to administer religious rites to the philosopher who had defended religion against philosophy. One man alone, his former secretary, attended the funeral. A Scotsman then in Hanover wrote that Leibniz “was buried more like a robber than what he really was, the ornament of his country.” 92
We must not spend space marking the flaws in this polymorphous multitude of ideas; time has long since performed these unpleasant obsequies. Critics have charged Leibniz with ubiquitous borrowing: they have found his psychology in Plato, his theodicy in the Scholastics, his monads in Bruno, his metaphysics, ethics, and mind-and-body relation in Spinoza. But who can say anything on these problems but what has been said a hundred times before? It is easier to be original and foolish than to be original and wise; there are a thousand possible errors for every truth, and mankind, with all its efforts, has not yet exhausted the possibilities. There is much nonsense in Leibniz, but we cannot quite decide whether it was honest nonsense or protective discoloration. So he tells us that when God created the world He saw in a flash, in its most minute detail, everything that was to happen in history. 93 “I always begin as a philosopher,” he said, “but I always end up as a theologian” 94—i.e., he felt that philosophy missed its aim if it did not lead to virtue and piety.
His long and genial debate with Locke gave him one of his many claims to significant thought. He may have exaggerated the innateness of “innate ideas,” but he admitted that they were capacities, instincts, or aptitudes rather than ideas; and he succeeded in showing that Locke’s sensationism had oversimplified the process of knowledge, and that “mind” is by its nature—if only crudely at birth—an organ for the active reception, manipulation, and transformation of sensations; here, as in his views of space and time, Leibniz stands high as a precursor of Kant. The doctrine of monads is shot through with difficulties (if they are not extended, how can any number of them produce extension? if they “perceive” the universe, how can they be immune to external influence?), but it was an illuminating attempt to bridge the chasm between mind and matter by making matter mental rather than mind material. Of course Leibniz failed to reconcile mechanism and design in nature, or mechanism in the body with freedom in the will; and his reseparation of mind and body after Spinoza had united them in one two-sided process was a step backward in philosophy. His pretense that this is the best of all possible worlds was the gallant or hopeful effort of a courtier to comfort a queen. The most learned of philosophers (“a whole academy in himself,” Frederick the Great called him) wrote theology as if nothing had happened in the history of thought since St. Augustine. But with all his shortcomings his achievements in science and philosophy were immense. Patriot and yet “good European,” he restored Germany to a high place in the development of Western civilization. “Of all who made Germany illustrious,” wrote Frederick II, “those rendering the greatest service to the human spirit were Thomasius and Leibniz.”95
His influence diminished as his theology lost face before the moral consciousness of mankind. Within a generation after his death his philosoph was given a systematic reformulation by Christian von Wolff, and in the modified form it became the dominant fashion of thought in the German universities. Outside Germany his influence was slight. Though most of his writings were in French, they were too fragmentary to exert any consistent or concentrated force; no collected edition appeared till 1768, and even then some important but heterodox items were excluded, and had to wait till 1901 to venture into print. His calculus notation was destined to victory, but for half a century his rivals, Newton and Locke, carried everything before them, and became the idols of the French Enlightenment. Yet even amid that ecstasy of reason Buffon ranked Leibniz as the greatest genius of his age. 96 The outstanding German thinker of the twentieth century, Oswald Spengler, considered Leibniz “without doubt the greatest intellect in Western philosophy.” 97
To round out these superlatives we may add that, all in all, the seventeenth century was the most productive in the history of modern thought. Bacon, Descartes, Hobbes, Spinoza, Locke, Bayle, Leibniz: here was a majestic sequence of men warm with the wine of reason, joyfully confident (most of them) that they could understand the universe, even to forming “clear and distinct ideas” about God, and leading—all but the last—to that heady Enlightenment which was to convulse both religion and government in the French Revolution. Leibniz foresaw that terminus; and while he continued to the end to defend freedom of speech, 98 he urged freethinkers to consider the effect of their spoken or written words upon the morals and spirit of the people. About 1700, in theNouveaux Essais, he uttered a remarkable warning:
If fairness wishes to spare persons (freethinkers), piety demands the representation, where it is fitting, of the bad effects of their dogmas when they are . . . contrary to [belief in] the providence of a perfectly wise, good, and just God, and contrary to that immortality of souls which renders them susceptible to the effects of His justice, not to speak of other opinions dangerous as regards morality and the police. I know that excellent and well-meaning men maintain that these theoretic opinions have less influence upon practice than is thought, and I also know that there are persons of an excellent disposition whom these opinions will never make do anything unworthy of themselves. . . . It may be said that Epicurus and Spinoza, for example, have led a life wholly exemplary. But these reasons cease most frequently in their disciples or imitators, who, believing themselves released from the troublesome fear of an overseeing Providence and of a menacing future, give loose reins to their brutish passions, and turn their minds to the seduction and corruption of others; and if they are ambitious, and of a disposition somewhat harsh, they will be capable, for their pleasure or advancement, of setting on fire the four corners of the earth. I have known this from the character of some whom death has swept away. I find also that similar opinions, insinuating themselves little by little into the minds of men of high life who rule others, and upon whom affairs depend, and slipping into the books of fashion, dispose all things to the general revolution with which Europe is threatened. 99
There is a spirit of sincere concern in these lines, and we must respect the counsel of caution that they express. And yet, even after the Enlightenment had crumbled creeds, and the French Revolution had set on fire the four corners of the earth, and the September massacres had transiently sated the thirst of the gods, a major historian could look back to this first age of modern science and philosophy and see its adventurers not as destroyers of civilization but as liberators of mankind. Said Lecky:
It was thus that the great teachers of the seventeenth century . . . disciplined the minds of men for impartial inquiry, and, having broken the spell that so long had bound them, produced a passionate love of truth which has revolutionized all departments of knowledge. It is to the impulse which was then communicated that may be traced a great critical movement which has renovated all history, all science, all theology—which has penetrated into the obscurest recesses, destroying old prejudices, dispelling illusions, rearranging . . . our knowledge, and altering the whole scope and character of our sympathies. But all this would have been impossible but for the diffusion of a rationalistic spirit. 100
So, for good or ill, the seventeenth century laid the foundations of modern thought. The Renaissance was tied to classical antiquity and to Catholic ritual and art; the Reformation was bound to primitive Christianity and a medieval creed. Now this rich and fateful era, from Galileo to Newton, from Descartes to Bayle, from Bacon to Locke, turned its face toward an uncharted future that promised all the dangers of liberty. It deserved, perhaps even more than the eighteenth century, the name Age of Reason; for though its thinkers were still the voices of a small minority, they displayed a wiser moderation, a deeper sounding of the limits and difficulties of reason and freedom, than the unmoored protagonists of the French Enlightenment. In any case the greatest drama in modern history had played its second act, and moved on to its fulfillment.