Opus doctore est, non tortore.
A teacher is what’s needed, not a torturer.
—Justus Lipsius, paraphrased
Giordano Bruno’s execution was designed to show the world that he had died a lone fanatic, not only defrocked and degraded by formal Church procedure, but also literally stripped bare of every worldly object before he was tied to the stake. If he had friends or sympathizers among the crowds who watched him burn to death, no one noticed them. Like the animals and people who were victims of the ancient Roman games, Giordano Bruno, or that part of him that had not been transformed into ether, was swept up with the ashes of his pyre and dumped into the Tiber. It would take a separate decree of the Holy Office to consign his writings, “every one of them”—“omnia scripta”—to the Index of Forbidden Books. And then Giordano Bruno was supposed to disappear.
But the reach of the Index stopped at the borders of Spain and Italy. Furthermore, a misprint in the Spanish version of the Index meant that in the Iberian Peninsula and the New World the forbidden author became “Iordanus Bruerus Holanus,” so that in theory some daring soul could have argued that no prohibition affected the reading of “Iordanus Brunus Nolanus.” There is no record, however, that anyone tried to do so. The error was reprinted, in issue after issue of the Spanish Index, suggesting that the list was neither read nor proofread with any particular care.
In Italy, meanwhile, powerful people could read whatever they liked. Francesco Cardinal Barberini, whose uncle Urban VIII led Galileo’s prosecution for heresy, owned a copy of Cause, Principle, and Unity. The library in the Jesuits’ Roman College must have contained several of Bruno’s books as well, because seventeenth-century Jesuit authors cite them.
An exchange between Kepler and Galileo in 1610 shows that Galileo had also read Giordano Bruno’s work on cosmology, and until 1601 it had been perfectly legal to do so. In 1610, when Galileo wrote his Starry Messenger to announce that the telescope had shown him moons around Jupiter and craters on the lunar surface, he sent a copy of the new book to Kepler in Prague. Kepler responded almost immediately in a long letter; this Galileo published in Florence as a small book in itself. In his letter, Kepler tellingly associates Bruno’s ideas about the infinite universe with prison and displacement, as if the philosopher’s thoughts automatically brought on the confinement and exile of which Bruno’s life had seemed to consist rather than, as Bruno had seen it, a deliverance from all bondage and all strangeness:
In the first place, I rejoice that you have restored me not a little by your labors. If you had found planets circling one of the fixed stars, there among Bruno’s infinities I had already prepared my prison shackles, that is, my exile in that Infinity. Thus you freed me from the great fear that I had conceived when I first heard about your book … because you say that these four planets run their course around Jupiter rather than one of the fixed stars.
Evidently, Kepler had no intention of giving up his own vision of a finite universe laid out according to musical intervals, until the day when observation would force him to revise it.
Another of Kepler’s comments to Galileo is, if anything, more revealing. The discoveries proclaimed by The Starry Messenger depended on the invention of a mechanical device, the telescope, in 1609. Making those observations, however, was by no means easy, and interpretation more difficult still. The Starry Messenger proves that Galileo was a superb technician, a superb observer, and a superb draftsman as well as an eloquent writer. His telescope boasted finer lenses than the Belgian original on which he based his design; his drawings of the moon’s surface are also extraordinary works of art. Some editions of The Starry Messenger show the constellation of the Pleiades bursting the margins of the page, just as contemporary cosmology was beginning to burst the margins of the universe. Yet Kepler tells Galileo that he himself is more impressed by the ingenuity of a thinker like Bruno, who predicted what the telescope would eventually reveal, than Galileo, who plied the telescope with such skill. Bruno’s gift for speculation, he suggests, is more truly godlike than Galileo’s empirical observations:
For the glory of this world’s Architect greatly exceeds that of the person, however ingenious, who contemplates it. The former, after all, drew the principles of its creation from within himself, whereas the latter, after great effort, scarcely recognizes the expression of such principles in that same creation. Certainly those who can conceive the causes of phenomena in their minds before the phenomena themselves have been revealed are more like Architects than the rest of us, who consider causes only after they have seen the phenomena. Do not, therefore, Galileo, begrudge our predecessors their proper credit … you refine a doctrine borrowed from Bruno.
Kepler’s admonition is not entirely fair; Galileo, writing in Italy, had good reason not to have mentioned his readings among Bruno’s banned books. Within six years, the Tuscan astronomer would be negotiating himself with Cardinal Bellarmine and the Holy Office. However, Kepler’s preference for speculation over experimentation was common to his time; Galileo, however strongly he advocated empirical observation, also made purely conceptual experiments. In fact, one of his most famous thought problems, involving motion, had also exercised Giordano Bruno.
Another of Galileo’s most vivid pronouncements had to do with the importance of mathematics to scientific investigation, although he calls this activity not science but philosophy in his 1623 book on comets, The Assayer:
Perhaps [my adversary] thinks that philosophy is a book, and one man’s imaginings, like the Iliad, and Orlando Furioso, books in which the least important matter is whether the contents are true. Signor Sarsi, it’s not like that. Philosophy is written in this great book that stands continually open before our eyes (I mean the universe), but you cannot understand it until you learn to understand its language, and know the script in which it is written. It is written in the language of mathematics, and the letters are triangles, circles, and other geometric figures, and without these means it is impossible for a person to understand one word; [to be] without them is to wander vainly through a dark labyrinth.
Galileo’s statement has been quoted ever since the eighteenth century because of its striking imagery, and because of the rigorous experimentation by which his science bore it out. Yet the idea that mathematics underpinned philosophy was as old as Pythagoras (and was so pervasive in Greco-Roman culture that the practical Roman architect Vitruvius could praise Plato first and foremost as a mathematician). In the generation before Galileo, Giordano Bruno had already made the same case for the preeminence of mathematics in philosophy. The Nolan philosophy, however, made scant use of calculations or empirical observations. Instead, it relied on mental geometries that are strange to us, and foresaw the need for new kinds of mathematics to account for the conditions of an expanded universe. Bruno’s mathematical world is in some respects entirely alien to modern science; in other respects (especially in the recognizably Platonic emphasis of string theory on unity and elegance) it is uncannily familiar.
Modern science, and the history of science, have emphasized the differences between Galileo and Bruno, but there are also profound similarities between the two, as both Johannes Kepler and Robert Bellarmine recognized from their different perspectives.
Another figure neglected until recently, the German Jesuit Athanasius Kircher, was also a reader of Bruno who presented elements of the Nolan philosophy to a wider public. Among a welter of fanciful ideas, Kircher also made some real progress in the sciences: he is now acknowledged as the inventor of plate tectonics, as the first person to propose a microbial origin for bubonic plague, and as the first scholar to suggest that Coptic, the liturgical language of Egyptian Christians, would provide the key to deciphering Egyptian hieroglyphics. With dozens of books to his name, many of them lavish picture books, he was also one of the most influential writers on natural philosophy in the entire seventeenth century, an author whose books were literally distributed worldwide through the global networks of the Society of Jesus.
As a literary figure, Bruno also continued to exert influence beyond his imprisonment and execution; his impact on Galileo’s Dialogue Concerning the Two Chief World Systems is evident in the later dialogue’s subject matter and its sparkling style. The extent of his effect on English literature is harder to gauge, but from Shakespeare’s Antony and Cleopatra to an early-seventeenth-century motet like Orlando Gibbons’s “O Thou, the Central Orb” (in which God is addressed as “the central orb of righteous love / pure beam of the on high / eternal light to this our bleak world”) it is possible to see glimmers of the Nolan philosophy.
By bearing steadfast witness to his own beliefs, Bruno also influenced the Church away from a policy of punishment toward a policy of persuasion. For the jubilee year of 1650, rather than scheduling the immolation of heretics, Pope Innocent X commissioned projects to beautify Rome, redecorating churches and installing a monumental fountain in Piazza Navona. There, thanks to the collaboration of the great sculptor Gian Lorenzo Bernini and the Jesuit Athanasius Kircher, an Egyptian obelisk stands above a travertine mountain whose slopes bear personifications of four rivers, representing four continents of the world, amid a burgeoning population of stone plants, animals, and sea monsters. At the obelisk’s peak flies a gilded bronze dove with an olive branch in its beak. The dove symbolizes the pope’s family, which had a dove in its coat of arms, but in 1650, with the Thirty Years’ War newly ended, it would be hard not to think about the dove in its usual role as a symbol of peace, as a kind of Christian hieroglyph of that idea. The fountain’s design, however, celebrates not so much the temporal peace of 1648 as peace of another kind: the partnership of natural philosophy—science—and religion. Only profound knowledge of nature’s laws could pump water into the middle of a city square in this profusion, or carve graceful texts into the surface of granite. But only faith could inspire the effort of carving granite in the first place. Mastery of physics keeps the obelisk standing above a hollow shell of travertine, but Bernini had no doubt that what guided his hand to create that hollow shell was divine inspiration. The Fountain of the Four Rivers simply could not exist if its makers did not believe that science and religion belonged together. Only a few blocks from the place where Giordano Bruno perished by fire, this assemblage of stone, water, and bronze suggests another kind of response to the challenges of his philosophy, joyful, generous, thoughtful, and surpassingly beautiful.