How Did the Church Respond to Heliocentrism?
The 1616 injunction, the 1633 condemnation of Galileo, the slow modification of the Index in 1662 and 1757, and the eventual Catholic acceptance of heliocentrism.
How Did the Church Respond to Heliocentrism?
The Catholic Church’s response to heliocentrism — the doctrine that the earth moves around the sun — unfolded over more than a century and a half, from the first circulation of Copernicus’s De revolutionibus in 1543 to the final removal of all heliocentric works from the Index Librorum Prohibitorum in 1757. The response was not a single decision but a long, uneven, internally contested process. It involved astronomers, theologians, cardinals, popes, and the Holy Office of the Inquisition, and it was driven by a complex mixture of biblical interpretation, Aristotelian natural philosophy, ecclesiastical politics, and pastoral concern. Understanding that process is essential to understanding the broader relationship between the new science and the Church. The brief version is that the Church initially treated heliocentrism with caution, then with suspicion, then with formal condemnation, and finally with grudging acceptance — a sequence that took 214 years from the publication of Copernicus to the final revision of the Index. The central episode in this long story was the trial and condemnation of Galileo in 1633. The story, told in its proper context, is more interesting than the simple caricature. For a broader account of the Church’s role in the Scientific Revolution, see The Scientific Revolution and the Church. For the deeper reasons for the Church’s resistance, see Why Did the Church Oppose Heliocentrism?. And for the background to the heliocentric doctrine itself, see Heliocentrism and Astronomy.
The First Reception of Copernicus
When Nicolaus Copernicus published De revolutionibus orbium coelestium in 1543, the book was read by few outside the small community of mathematical astronomers. The dedication to Pope Paul III, in which Copernicus explained that he had waited “not only nine years, but into the fourth nine-year period” before publishing, contained a careful disclaimer: he was not committing himself to the truth of the heliocentric hypothesis, only offering it as a mathematical device for computing the positions of the planets with greater convenience. The book was, on its surface, a technical work of astronomy, written in Latin, addressed to professional astronomers. The preface, however, was not by Copernicus. It was an unsigned introduction by Andreas Osiander, a Lutheran theologian who had overseen the printing of the book in Nuremberg. Osiander’s preface — “To the reader, concerning the hypotheses of this work” — explicitly framed the heliocentric system as a hypothesis, not as a claim about the real structure of the cosmos. Copernicus himself, in the published text, did not endorse this framing, and later editions of the book, especially after the 1616 condemnation, treated Osiander’s preface as a misrepresentation of the author’s views. The early Catholic reception of Copernicus was cautiously positive. The Dominican Giovanni Maria Orlandi wrote a letter to Copernicus shortly before the latter’s death, expressing approval of the new astronomy. The Jesuit scholars, who dominated Catholic higher education in the late sixteenth century, taught a hybrid of Ptolemaic and Copernican astronomy in some of their colleges. The mathematician and astronomer Christopher Clavius, the leading Jesuit astronomer of the late sixteenth century, was broadly sympathetic to Copernicus, though he stopped short of endorsing the heliocentric hypothesis. There was, in the 1540s and 1550s, no clear Catholic prohibition on reading or teaching Copernicus.
The Protestant Objections
The first explicit religious objection to heliocentrism came not from the Catholic Church but from the Protestant reformers. Martin Luther, in his Table Talk of 1539, dismissed Copernicus as “a fool” who wished “to reverse the entire science of astronomy” and asserted that sacred scripture showed Joshua had commanded the sun, not the earth, to stand still. John Calvin, more cautiously, declined to commit himself on the astronomical question but insisted that the earth could not be moved without doing violence to the Psalmist’s description of the sun running its course. These reactions did not lead to formal Protestant prohibitions on Copernicanism, but they set a tone that would persist in some Protestant circles well into the seventeenth century. The more consequential Protestant contribution to the controversy came from a different direction. The Calvinist theologian and biblical commentator Andreas Rivetus, and the Lutheran theologian Abraham Calov, both wrote extensive critiques of the Copernican system in the mid-seventeenth century, on grounds of biblical authority. Their arguments were similar in form to the Catholic arguments but had no central authority to enforce them. Protestant acceptance of heliocentrism proceeded slowly and unevenly. By the late seventeenth century, most Protestant astronomers had accepted the heliocentric system, but a vocal minority continued to oppose it on scriptural grounds, and the controversy persisted into the eighteenth century in some German Lutheran communities.
The 1616 Injunction
The Catholic Church’s formal engagement with heliocentrism began in 1610, when Galileo Galilei, using the newly invented telescope, published his Sidereus Nuncius — the Starry Messenger — in which he reported observations of the moons of Jupiter, the irregular surface of the moon, and many new stars invisible to the naked eye. The observations, which were quickly confirmed by other astronomers, supported the Copernican system and damaged the Ptolemaic. In December 1610 and January 1611, Galileo made further telescopic discoveries: the phases of Venus (which the Ptolemaic system could not easily explain but the Copernican could), and (in 1611) sunspots. The response from the Church was initially cautious. In 1611 Galileo visited Rome and was received with great honor. He had private conversations with several high-ranking churchmen, including Cardinal Robert Bellarmine, one of the most influential theologians of the age. Bellarmine, in a letter of 1615, set out the standard position of the Church on the relationship between scripture and natural philosophy: if a demonstrative proof of the earth’s motion were produced, the Bible would have to be reinterpreted, since “the Holy Ghost did not intend to teach us how the heavens go, but how to go to heaven.” But, Bellarmine continued, no such demonstrative proof had yet been produced, and in the absence of such a proof, the traditional reading of the relevant biblical passages had to stand. In February 1616 the Holy Office formally examined the Copernican doctrine. On February 5, the Qualifiers of the Holy Office reported that the proposition that the sun is at the center of the world and the earth moves is “formally heretical” because it contradicts the literal sense of scripture. On February 25, the Holy Office instructed Copernicus’s De revolutionibus to be “suspended until corrected” — that is removed from circulation until certain passages were modified. Galileo was privately admonished by Bellarmine not to hold or defend the Copernican opinion. The stage was set for the more dramatic events of 1633.
The Trial of Galileo (1633)
The trial and condemnation of Galileo in 1633 is the most famous episode in the long history of the Church’s engagement with heliocentrism. The story is told in the article on the Trial of Galileo; the present account focuses on the Church’s policy on heliocentrism as a whole. In 1623 Maffeo Barberini, a friend and admirer of Galileo, was elected pope as Urban VIII. The new pope, who had written a poem in praise of Galileo’s telescopic discoveries, gave Galileo permission to write a comparative discussion of the Ptolemaic and Copernican systems, on the condition that the treatment be neutral and reach no final conclusion. The result was the Dialogue Concerning the Two Chief World Systems (1632), which, despite its official disclaimer, was read by contemporaries as a defense of Copernicanism. The book was referred to the Inquisition, and Galileo was tried in 1633 on charges of heresy. He founded “vehemently suspect of heresy,” forced to recant, and sentenced to house arrest, where he remained until his death in 1642. The Dialogue placedd on the Index of Prohibited Books in 1634. The Epitome of Copernican Astronomy by Johannes Kepler, published in 1618–1621, was also placed on the Index in 1619. The formal Catholic position from 1633 until 1757 was that the heliocentric doctrine was false in fact and heretical in theology, and that Catholics were forbidden to read, teach, or defend it.
The 1662 Revision of the Index
The first significant modification of the formal Catholic prohibition on heliocentrism came in 1662. In 1661 the Sacred Congregation of the Index, after consultation with the Holy Office, issued a decree modifying the prohibition on Copernicus’s De revolutionibus. The modified version, published in 1662 with a preface by the Master of the Sacred Palace, declared that the heliocentric doctrine was indeed contrary to scripture and could not be held as true, but permitted the reading and discussion of the work by experts as a mathematical hypothesis. The prohibition on teaching heliocentrism as true remained in force. The 1662 modification reflected several developments. The work of Descartes, Gassendi, and (most importantly) Newton had by then established a mechanical natural philosophy in which the motion of the earth was mathematically tractable, and in which the absence of observational refutation would becoming difficult to explain on Ptolemaic grounds. The telescope had also produced ever more evidence in favor of the Copernican system. And the institutional weight of the Jesuits, who had long been sympathetic to the new astronomy in their own colleges, would beginning to tell on the policy of the Index.
The Eighteenth Century: Toward Acceptance
The slow acceptance of heliocentrism by the Catholic Church in the eighteenth century was driven by a combination of intellectual and institutional factors. The Newtonian synthesis, disseminated through Catholic Europe by writers such as Voltaire and the Jesuit physicist Roger Boscovich, made heliocentrism a centerpiece of the new physics. The work of Catholic astronomers — notably Giovanni Domenico Cassini in Paris, who directed the new Paris Observatory, and the Jesuit astronomers of the Roman College — produced observations that could not be reconciled with the Ptolemaic system. And the general climate of the Enlightenment made the formal condemnation of heliocentrism increasingly untenable. In 1741 Pope Benedict XIV, who was both a scholar and a reformer, commissioned a study of the heliocentrism question. The study, completed in 1742, recommended that the prohibition be lifted. The full lifting took another fifteen years, in part because of resistance within the Index and the Inquisition, and in part because the pope wanted to handle the matter carefully. On July 16, 1757, the Sacred Congregation of the Index issued a new decree permitting the reading and discussion of all books teaching heliocentrism, including those that taught it as true. The decree was not publicly announced in a way that would draw attention to the change, but the prohibition was effectively at an end. The formal condemnation of the Dialogue by the Index remained in force until 1835, when, in a general revision of the Index under Pope Gregory XVI, Galileo’s book was finally removed. And it was not until 1992, more than 350 years after the trial, that Pope John Paul II formally acknowledged that the Church had erred in its treatment of Galileo. The long aftermath of the Galileo affair, in other words, is still being worked out.
Protestant Astronomers and the New Heliocentrism
The Protestant response to heliocentrism in the seventeenth and eighteenth centuries was, in the absence of a central authority, much more varied than the Catholic response. The major Protestant astronomers — Tycho Brahe in Denmark, Johannes Kepler in Germany, Christiaan Huygens in the Netherlands, Edmond Halley and Isaac Newton in England — were all Copernicans. The German Lutheran universities were slower to accept the new astronomy, but by the late seventeenth century the heliocentric system was being taught in most of them. A particular case is the growth of the Tychonic system, the geo-heliocentric hybrid in which the sun and moon revolve around the earth, while the other planets revolve around the sun. The Tychonic system, proposed by Tycho Brahe in the 1580s, was observationally equivalent to the Copernican system but did not require the motion of the earth. It was adopted by many Catholic and Protestant astronomers who wished to preserve the geocentric worldview while accepting the telescopic evidence. The system was eventually abandoned as the evidence for the earth’s motion accumulated, but for a time it offered a useful middle ground. The deeper theological engagement of the Protestant churches with the new cosmology was conducted in a more decentralized way than the Catholic engagement, and it produced a wider range of positions. The Lutheran natural philosopher and theologian Paul Eber, for example, accepted the heliocentric system and wrote that the Bible, properly interpreted, was compatible with it. The Calvinist theologian and natural philosopher Jean-Alphonse Turrettini in Geneva accepted the system and argued that the Bible was a book of salvation, not of natural philosophy. By the early eighteenth century, the heliocentric system was broadly accepted in the Protestant world, both as a matter of astronomy and as a matter of theology.
The Slow Acceptance as a Cultural Process
The slow acceptance of heliocentrism was not just a matter of papal decrees and theological argument. It was a cultural process, in which the new cosmology gradually displaced the old in the imagination of European readers, writers, and teachers. By 1700, the heliocentric system was being taught in most European universities, even in some Catholic institutions where the official teaching remained Ptolemaic. By 1750, the heliocentric system was a standard feature of encyclopedias, popular lectures, and coffee-house conversation. By 1800, the system was so well established that the previous controversy would beginning to be forgotten, and the Galileo affair would becoming the stuff of legend. The long delay in the formal Catholic acceptance of heliocentrism — more than two centuries from Copernicus to the final Index revision — is sometimes taken as evidence of the Church’s hostility to science. The delay is real, but it should be understood in the context of the time it took for the heliocentric system to be established as a matter of demonstrative science. Until Newton’s Principia of 1687 provided a mechanical account of the solar system in which heliocentrism was a consequence of the laws of motion and universal gravitation, the heliocentric hypothesis remained, in the eyes of many, a hypothesis — observationally well supported but physically unexplained. The full acceptance of heliocentrism required not just the telescopic evidence that had been accumulating since 1610 but the new physics that explained why the earth moves around the sun. The Church’s slowness, in other words, was not simply a matter of theological conservatism; it was also a matter of waiting for the science to settle.