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  In December 1610, Galileo announced a startling new discovery. Venus exhibited phases, like the moon. He presented this finding as strong evidence in favor of Copernicus.

  Astronomers since antiquity knew that Venus always stayed close to the sun. Supposedly Pythagoras had discovered that what appeared to be two separate stars—the morning and evening stars, each appearing near the sun—were actually one planet: Venus.47 Even if Venus were traveling on an epicycle, it would never be on the side of the heavens opposite to the sun. Therefore, in Ptolemy's system, Venus should never seem to reflect a fully sunny face onto Earth. By the 1600s, Ptolemy's system had been construed in various versions: in some, the orbit of Venus was beneath the orbit of the sun; in other versions, its orbit was above the orbit of the sun, and in others, Venus did not travel on any epicycle. In none of these geocentric accounts could Venus exhibit the sequence of phases that Galileo observed through his telescope. Instead, he saw phases corresponding to the motion of Venus around the sun. He concluded that the phases of Venus showed the truth of the Copernican system.

  Galileo's findings were startling and quickly gained public attention, yet there was plenty of skepticism, and most people remained unconvinced. Some professors did not believe in the images produced by Galileo's telescope. Some even refused to look into his instrument. Thus he complained to Kepler, in a letter: “My dear Kepler, I wish we could laugh at the extraordinary stupidity of the mob. What say you about the foremost philosophers of this University, who with the obstinacy of a stuffed snake, and despite my attempts and invitations a thousand times they have refused to look at the planets, or the Moon, or my telescope?”48 Still Galileo continued to refine his instrument and to make new observations. He used it to project images of the sun and found, surprisingly, that the sun had spots. It was not a perfectly uniform body as people thought. Plus, the spots were moving! He found that the spots moved all around the sun in about twenty-seven days and concluded that the sun must be spinning on its axis. Therefore, he inferred, this proved that at least some heavenly bodies do spin; thus, that Earth also spins, just as Copernicus had claimed. Again Galileo's claims were criticized. For example, Christoph Scheiner, a Jesuit, hypothesized that the spots were not on the sun itself, but consisted instead of swarms of moons.

  Despite such disparagement, Galileo's refined image of the universe took shape. It was basically the account advanced by Copernicus, but Galileo added four moons onto Jupiter and also advanced the notion that the sun spins at the center of the universe. To some people, the Copernican account seemed to clash with the Bible, which includes passages that refer to the motion of the sun. Kepler and Galileo did not consider this a problem, because they argued that Holy Scripture was written in the language of human perceptions, just as today we still say that the sun rises in the morning. According to Kepler and Galileo, the Bible was not meant to teach about astronomy, and astronomy could be pursued in the service of Christianity, to better understand Scripture.

  A problem, however, was that the various churches were fighting over how to properly interpret Scripture. Since 1546, in the Council of Trent, the Catholic Church had attributed to itself alone the right to interpret Scripture, contrary to the church reformers' claim that the Bible could be comprehended by individuals who read it literally. The “heretics” claimed the right to read God's book; Galileo, in 1613, claimed the right to read the book of nature, “this great book of the world,” against the interpretations of Aristotle.49 And Galileo's opinions were disrespectful to the Jesuits. Galileo was a devout Catholic, but he implied that astronomers and mathematicians could understand God's creation independently of the decrees of theologians.

  Meanwhile, in Naples, a Father of the Carmelite Order wrote a defense of “the opinion of Pythagoras and of Copernicus.” Father Paolo Antonio Foscarini admitted that their opinion that the Earth moves seemed to be “sheer madness” and “one of the oddest and most monstrous paradoxes”—but, that it was denied mainly by habit rather than reason and that new astronomical evidence might well show, again, that “the majestic white beards of the ancients were wrong; they have been believed too easily and their false imaginations solemnized.”50 Foscarini argued at length that the Pythagorean opinion could be reconciled with the various Biblical passages that seem to say that Earth does not move and so forth. He denounced the patchwork of spheres and circles: “epicycles, equants, deferents, eccentrics, and a thousand other fantasies and chimeras, which are more like beings of reason than real things.”

  Despite explicitly submitting his argument reverently to the judgment of the Holy Church, Foscarini quoted a line from the Epistles of Horace: “I am not bound to swear as any master dictates,” because he argued that whereas the Church could not possibly err in matters of faith and salvation, it could err in practical and philosophical judgments.51 Foscarini explained that the Bible includes various metaphors and common ways of speaking, such as when it refers to God as walking, having a face, eyes, anger, and similar images, or to death as eating, moving, having a voice, and having a shadow. He defended the “monstrous and extravagant” notion that hell, at Earth's center, revolves through heaven around the sun by insisting that the heavens of the planets are distinct from the spiritual heaven, which is above everything. In light of the findings of Copernicus, Kepler, and Galileo, Foscarini concluded that the opinion of Pythagoras was quite probable and not necessarily in conflict with Scripture.

  Responding to accusations against Foscarini and Galileo, the Catholic Church intervened. The Inquisition met in 1616 to discuss the Copernican theory. Cardinal Roberto Bellarmino, who had been the inquisitor in the deadly trial against Giordano Bruno, participated. There is a recurring myth to the effect that the Catholic theologians were mainly annoyed by the notion that humanity was not literally the center of God's creation—but historical research shows no evidence of that.52 The center of the universe, inside Earth, was not a particularly privileged place to Catholics such as Bellarmino, who believed it to be the actual location of hell.53 The Copernican scheme seemed offensive because Galileo advocated it as a source of authority for interpreting Scripture, against the interpretations of the Church leaders. Cardinal Bellarmino noted that, although the subject matter of Earth's motion was indeed not a subject of faith, it was yet a matter of faith on the speakers: the apostles, prophets, and commentators, who had all agreed that the sun is in the heavens and moves around Earth. Bellarmino argued that, there being yet no proof, no demonstration of Earth's motion, it was inappropriate to abandon the traditional interpretation of Scripture or to depart from the Council of Trent.54

  In 1616, the Holy Congregation denounced “the false Pythagorean doctrine, altogether contrary to Holy Scripture.”55 The cardinals concluded that the proposition of a stationary sun is “foolish and absurd in philosophy, and formally heretical since it explicitly contradicts in many places the sense of Holy Scripture, according to the literal interpretation of the words.”56 Therefore, the sun-centered theory could not be defended or held. The Holy Congregation promptly banned the books of Copernicus and Zuñiga until each could be corrected. More forcefully, to defend Catholic dogma, the Holy Congregation “completely prohibited and condemned” Foscarini's Pythagorean booklet and all future works like it.57 Similarly, inquisitors banned Galileo from believing in Copernican ideas, and Cardinal Bellarmino gave Galileo a certificate forbidding him from believing or defending the idea that Earth moves. But Galileo surmised that he could at least entertain and teach the theory as a speculative hypothesis. After all, the clergymen acknowledged that the scheme of Copernicus had certain mathematical advantages: it simplified calculations of the positions of the planets.

  Meanwhile, Kepler faced other troubles. His wife suffered from Hungarian spotted fever and epileptic seizures. Three of his children had died, and later his wife died too. He remarried, but then three more newborns died. He also had religious problems. Kepler was a Lutheran but he wanted a reconciliation among the divisions of Chri
stianity: “It makes me heartsick that the three big factions have so miserably torn up the truth among themselves.”58 Kepler refused to sign the Formula of Concord, the orthodox beliefs that were allegedly required of all Lutherans. (In fact, some Lutherans did not accept it, almost half of the ministers who prepared the document did not sign it.) He mainly disagreed with their claim that the physical body and blood of Jesus Christ actually combines with the bread and wine in the ceremony of the Eucharist. The Lutherans had denied the Catholics' idea of transubstantiation: that bread and wine literally become the body and blood of Christ. The Lutherans asserted instead the so-called “sacramental union” (or consubstantiation): that four substances combine during the ceremony: bread with the body of Christ, and wine with His blood. Kepler disagreed and sympathized instead with the Calvinist idea that the Eucharist was essentially a symbolic commemoration infused by the spiritual presence of Christ. Kepler still wanted to take communion; he argued that this was a minor disagreement. But the Lutheran ministers disagreed. In 1619, they excommunicated him from their Church, to his chagrin.59

  That same year, the Catholics banned Kepler's Copernican writings. Not only had Kepler affirmed the reality of the Copernican system, he openly pondered numerology and voiced his theological opinions. He argued that mathematics contains hidden divine knowledge: “Plato teaches us many remarkable things about the nature of the gods through the appearance of mathematical things; and the Pythagorean philosophy disguises its teaching on divine matters with these, so to speak, veils.”60 Kepler conjectured that the ancient Pythagoreans had known and hidden the connection between five regular solids and the order of the planets.61 He also argued against Aristotle and Cicero for having denied that the heavens generate inaudible harmonies: “These preconceived opinions are a considerable obstacle to readers who are striving towards the inner secrets of Nature, and could frighten off many who have great powers of judgment and are seekers after truth, to such an extent that they would disdain those Pythagorean pipedreams, scarcely recognized at arm's length, and throw away the book unread.”62

  At the same time, Kepler had to deal with legal attacks upon his mother, who was accused of being a witch. His great-aunt had earlier been burned at the stake for witchcraft. And for seven years, superstitious townspeople and neighbors spread gossip and suspicions against Kepler's wrinkled old mother. “The lies had been repeated so many times by so many people that they had begun to be accepted as truth.”63 His mother—allegedly—had poisoned people with potions, she rode a calf to death, she terrorized livestock, and she had injured and killed children by touching them. Gossip became admitted into prosecution records. Actually, she had at least done a few odd acts, such as asking a gravedigger for her father's skull, which was illegal, to make a goblet for her son. For years, Kepler defended his mother against forty-nine articles that could have led to her execution. Still, she was sentenced to be verbally terrorized by the executioner showing his instruments of torture so that she would confess to witchcraft. But she did not. Finally they exonerated her of the charges. But then promptly she died in 1622. And in 1623, another newborn son of Kepler died.

  Meanwhile, Galileo continued to pursue the Copernican theory as if it were true, despite having said that he would accept the decrees of the Inquisition. He also continued to argue as if there were paths to truth independent of the authority of the Catholic Church. In 1623, he wrote:

  Philosophy is written in this grand book, the universe, which stands continually open to our gaze, but the book cannot be understood unless one first learns to comprehend the language and read the letters in which it is composed. It is written in the language of mathematics, and its characters are triangles, circles, and other geometric figures without which it is humanly impossible to understand a single word of it; without these, one wanders about in a dark labyrinth.64

  Again, he seemed to be saying that mathematicians such as himself had a special skill for understanding nature, the work of God.

  At the same time, a friend of Galileo, Maffeo Barberini, was elected as the new leader of the Catholic Church, becoming Pope Urban VIII in 1623. Galileo subsequently was kindly invited to papal audiences on six occasions. Thus, he seems to have grown bolder in his confidence that the Copernican account might eventually be favored. Meanwhile, Kepler, though ill, planned to finally publish his belated but much expanded “dream” about the moon. But he died in 1630, survived by his second wife and six children.

  In 1632, the sixty-eight-year-old Galileo published his Dialogue on the Two Chief Systems of the World—Ptolemaic and Copernican. In it, Galileo portrayed a discussion among three characters, one of whom argued persuasively in favor of the Copernican theory. The character who defended the Aristotelian views appeared as an idiot. Promptly thereafter, Galileo was summoned by the Inquisition to a trial in Rome to determine whether he had violated the conditions of its 1616 decrees.

  Pope Urban VIII became bitterly enraged that Galileo had deceived him, that Galileo “dared entering where he should not have, into the most serious and dangerous subjects which could be stirred up at this time…. matters, involving great harm to religion (indeed the worst ever conceived),…. the most perverse subject that one could ever come across.”65 Likewise, representatives of the Society of Jesus said that Galileo's vile book was “more harmful to the Holy Church than the writings of Luther and Calvin.”66 But why? How could anyone say that? Were they just exaggerating? The Catholic Church had lost half of Europe because of the influence of Luther and Calvin. How could a scientific question such as Earth's motion seem in any way more dangerous than the transgressions of the heretics? Having studied this issue for years, I still could not understand why. Finally I realized that one particular word has some neglected significance. Pythagorean.

  Consider again the Decree of the Inquisition of 1616, which banned “the false Pythagorean doctrine, altogether contrary to Holy Scripture.” Historians and scientists have read this as an allusion to an ancient tradition of mathematicians, scientists and astronomers.67 As usual, writers give no evidence that Pythagoras really ever claimed that the Earth moves; as there is none. But what about the religious connotations? If instead the sentence read, “the false Lutheran doctrine, altogether contrary to Holy Scripture,” it would be evident that there was some religious issue here. But since the Pythagorean profile has been reinterpreted over centuries, this religious dimension seems to have become invisible.

  Nowadays, Pythagoras is mostly portrayed as an ancient Greek mathematician. But that is a fame that he did not clearly deserve. Instead, in ancient times, and for many centuries, he was known primarily as the leader of a secretive religious cult that believed in multiple lives after death. They praised Pythagoras as a demigod.

  Perhaps the Catholic theologians who disparaged Galileo's heliocentric ideas as “Pythagorean” surmised a repulsive threat. Pythagoras was an alien pagan influence: he worshipped Greek gods, especially the sun god, Apollo.68 One ancient poem claimed that Pythagoras was the son of Apollo, who visited his mother: “Pythagoras, whom Pythias bore for Apollo, dear to Zeus, she who was the loveliest of the Samians.”69 Iamblichus claimed that Pythagoras was “the most handsome and godlike of those ever recorded in history.”70 Above all, Pythagoras was a superhuman sent from the domain of Apollo to enlighten mortals to live properly. Early Christian Church fathers vigorously criticized Pythagorean philosophy as heresy and lies, in which “the Creator of all alleged existence is the Great Geometrician and Calculator a Sun; and that this one has been fixed in the whole world”—and they denounced various heretics as “disciples not of Christ but of Pythagoras.”71 Whereas Christians believed that Jesus and only Jesus had reincarnated, supposedly Pythagoras had been reborn several times. And Pythagoras taught that other human souls are also reborn repeatedly, even in animals. Allegedly he taught that human souls come from the Milky Way, where the infernal regions begin, and that animal souls come from the stars.72 And he apparently taught that we should no
t eat flesh, but the Bible told believers to eat meat, and at Mass Christians ate the body of Christ. Allegedly Pythagoras had performed many miracles too.73 His supposed teachings and divine revelations were featured, for instance, in Ovid's pagan poem Metamorphoses.74 Diogenes Laertius noted that Pythagoras theorized that “the Sun, and the Moon, and the stars were all Gods” and echoed that Pythagoras “was actually the god Apollo, and that he had spent two hundred and seven years in the underworld, had there seen all the men who ever died (“he saw the soul of Hesiod bound to a brazen pillar, and gnashing its teeth; and that of Homer suspended from a tree, and snakes around it, as a punishment”), that he remembered his sufferings in hell—and that Pluto, god of the dead, ate only with the Pythagoreans.75

  Porphyry too, a staunch advocate of polytheism, celebrated Pythagoras as a moral and divine superhuman, more eminent than anyone.76 In one of his earliest works, Porphyry claimed that the god “Apollo exposed the incurable corruption of the Christians, saying that the Jews, rather than the Christians, recognized God.”77 Porphyry's notorious fifteen-volume work Against the Christians was banned by the first Christian Roman emperor; nearly all copies were destroyed by the Christians, burned, only fragments remain.78 Because of his extensive, historical-critical attacks, Porphyry became known as one of the greatest early enemies of Christianity; his name became synonymous with blasphemy. When Pope Leo X condemned the writings of Martin Luther as “blinded in mind by the father of lies,” the Devil, he denounced Luther as “a new Porphyry.”79 Saint Augustine, in his widely read City of God Against the Pagans, had criticized Pythagoras for being a necromancer, one who tried to divine the future by communicating with inhabitants of the netherworld: the dead, or demons pretending to be gods.80