Was he himself a Christian? Outwardly yes, of course; a man with his zeal to pass from philosophy to statesmanship had to robe himself in the theology of his time and place. “I have endeavoured in all things,” said his preface to the Theodicy “to consider the need for edification.” 16 The writings that he published during his life were exemplary in their faith; they defended the Trinity, miracles, divine grace, free will, immortality; and they attacked the freethinkers of the age as undermining the moral bases of social order. However, “he went to church little . . . and for many years did not communicate”; 17 the simple people of Hanover nicknamed him Lövenix (i.e., glaubt nichts—believes nothing). 18 Some students have credited him with two opposed philosophies: one for public consumption and the comforting of princesses; the other “a clear-cut affirmation of all the principles of Spinozism.” 19 “Leibniz fell into Spinozism whenever he allowed himself to be logical; in his published works, accordingly, he took care to be illogical.” 20
His efforts to reconcile Catholicism and Protestantism subjected him to the charge of indifferentism. 21 His passion for unity and compromise dominated his theology; while avoiding preachers, he labored to bring them together. Because he saw deeply he minimized surface diversities; if Christianity was a form of government, its creedal varieties seemed to him not instruments of piety and good will but obstacles to order and peace.
In 1677 the Emperor Leopold I sent Christopher Rojas de Spinola, titular bishop of Tina in Croatia, to the court of Hanover to suggest to the Duke, John Frederick, himself a convert to Catholicism, that he join in a campaign to reunite Protestants with Rome. Probably the plan had political fringes: the Elector at the time desired the support of the Emperor, and Leopold hoped for a stronger German unity and spirit against the Turks. For a while Spinola commuted between Vienna and Hanover, and the affair progressed. When Bossuet (1682) formulated the Gallican Declarations by which the French clergy defied the Pope, Leibniz may have been led to hope that France would join with Germany in a Catholicism sufficiently independent of the papacy to soften Protestant hostility to the ancient creed. In 1683, as the Turks were marching to the siege of Vienna, Spinola assembled at Hanover a conference of Protestant and Catholic theologians, and submitted to them “rules for the ecclesiastical union of all Christians.”
It was probably for this meeting 22 that Leibniz anonymously composed the strangest of the many documents that were found among his papers after his death. It was called Systema Theologicum, and purported to be such a statement of Catholic doctrine as any Protestant of good will might accept. In 1819 a Catholic editor published it as evidence that Leibniz had been secretly converted; more likely it was a diplomatic effort to reduce the theological gap between the two communions, but the editor was justified in considering the paper overwhelmingly Catholic. It began with brief impartiality:
After invoking the divine aid by long and earnest prayer, putting aside, so far as is humanly possible, all party spirit, looking at the religious controversies as though I had come from another planet, a humble learner, unacquainted with any of the various communions, bound by no obligations, I have, after due consideration, arrived at the conclusions hereinafter set forth. I have deemed it incumbent upon me to embrace them because Holy Writ, immemorial religious tradition, the dictates of reason, and the sure testimony of the facts, seem to me to concur in establishing them in the mind of any unprejudiced human being. 23
Thereupon followed a profession of faith in God, Creation, original sin, purgatory, transubstantiation, monastic vows, invocation of saints, use of incense, religious images, ecclesiastical vestments, and the subordination of the state to the Church. 24 This generosity to Catholicism might cast doubt on the document, but its authenticity as a work of Leibniz is generally accepted today. 25 Perhaps he hoped, by so supporting the Catholic view, to prepare for himself a commodious berth at the court of the Catholic Emperor in Vienna. And, like any good skeptic, Leibniz admired the sight, sound, and smell of Catholic ritual.
Thus the strains of music, the sweet concord of voices, the poetry of the hymns, the beauty of the liturgy, the blaze of lights, the fragrant perfumes, the rich vestments, the sacred vessels adorned with precious stones, the costly offerings, the statues and the pictures that awaken holy thoughts, the glorious creations of artistic genius, . . . the stately splendor of public processions, the rich draperies adorning the streets, the music of bells, in a word all the gifts and marks of honor which the pious instincts of the people prompt them to pour forth with lavish hand, do not, I trow, excite in God’s mind the disdain which the stark simplicity of some of our contemporaries would have us believe they do. That, at all events, is what reason and experience alike confirm. 26
All these arguments failed to move the Protestants. Louis XIV disrupted the décor by revoking the Edict of Nantes and making brutal war upon French Protestants. Leibniz set aside his agape for more gracious times.
In 1687, to consult scattered archives for his Annals of the House of Brunswick, he set out on three years of travel through Germany, Austria, and Italy. In Rome, on the assumption that he would accept conversion, the authorities offered him the curatorship of the Vatican Library; he declined. He made a brave attempt to obtain cancellation of the ecclesiastical decrees against Copernicus and Galileo. 27 After his return to Hanover he began (1691) three years of correspondence with Bossuet in the hope of reviving the movement for the reunion of Christendom. Could not the Roman Church call a really ecumenical council, one including Protestant as well as Catholic leaders, to reconsider and revoke the Council of Trent’s harsh branding of Protestants as heretics? The bishop, who had just bombarded these “heretics” with his Variations des églises protestantes (1688), replied uncompromisingly: if the Protestants wished to re-enter the sacred fold, let them accept conversion and end the debate. Leibniz begged him to reconsider. Bossuet held out hope: “I enter into the scheme. . . . You shall shortly hear what I think.” 28 In 1691 Leibniz wrote to Mme. Brinon with his usual optimism:
The Emperor is favorably disposed; Pope Innocent XI and a number of cardinals, generals of monastic orders, . . . and many grave theologians, having carefully considered the matter, have expressed themselves in the most encouraging terms. . . . It is no exaggeration to say that if the King of France and the prelates . . . who have his ear in this matter were to take concerted action the thing would not be merely feasible, it would be as good as done. 29
When Bossuet’s answer came it was crushing: the decisions of the Council of Trent were irrevocable; they had rightly held the Protestants to be heretics; the Church is infallible; no conference between Catholic and Protestant leaders could reach any constructive result unless the Protestants would agree in advance to adopt the decisions of the Church on the matters at issue. 30 Leibniz replied that the Church had often changed her views and teaching, had contradicted herself, and had condemned and excommunicated persons without just cause. He declared that he “washed his hands of all responsibility for whatever further ills the existing schism may have in store for the Christian Church.” 31 He turned to the apparently more hopeful task of reconciling the Lutheran and Calvinist branches of Protestantism, but here he met with an intransigence as hard and proud as Bossuet’s. At last he privately called down a plague upon all the rival theologies, and proclaimed that there were only two kinds of books with any value: those reporting scientific demonstrations or experiments, and those containing history, politics, or geography. 32 Outwardly, and laxly, he remained a Lutheran to the end of his life.