Science in Christian Perspective

The Censorship of Copernicus'De revolutionibus
Owen Gingerich
Harvard-Smithsonian Center for Astrophysics
Cambridge, Massachusetts 02138

From: JASA 33 (March 1981): 58-60.
By the end of the sixteenth century Copernicus' De revolutionibus orbium coelestium was securely established as an important book, undoubtedly the most significant astronomical treatise since antiquity. The two editions of the work, Nuremberg 1543 and Basel 1566, were by then widely distributed throughout Europe in several hundred copies each; at least one copy had reached America and another would soon arrive in China. A bulky work of 400 pages and well illustrated with 146 diagrams, it was too imposing to be discarded lightly and too formidably technical to be worn out from overuse. As we shall see, this unique book received unique treatment from the Inquisition.

The initial reaction of the church, both Catholic and Protestant, was muted. The often-quoted comment from Luther's Table Talk, that "this fool would turn the whole art of astronomy upside down" (or, in the alternative version, that everyone who would be clever nowadays must come up with something new), is grossly misleading. A casual remark, Luther's off-the-cuff judgment is not at all representative of the actual Lutheran reaction. In fact, Copernicus' book was highly regarded in Lutheran circles and extensively studied throughout their university system.

The potential ecclesiastical reaction to Copernicus' radical heliocentric cosmology was considerably tempered by the anonymous introduction added in publication by Andreas Osiander, a Luther clergyman of Nuremberg hired by the printer to oversee the final stages of the proofreading. Osiander's introduction stated that the hypotheses of the work "need not be true nor even probable," and that their essential requirement was to furnish a model whereby planetary positions could be calculated for any conceivable time. That this was precisely the way the book was received in the Lutheran universities is admirably borne out by the pattern of annotations found in a score of well-studied books.

It was within this framework that Johannes Kepler learned about De revolutionibus from his Tiibingen teacher, Michael Maestlin. Shortly thereafter the young Kepler took a post as a high school mathematics teacher in southern Austria, and it was there in 1597 that he received the copies of his new book, the Mysterium Cosmographicum, the first unabashedly heliocentric treatise to appear since Copernicus had published his De revolutionibus over fifty years previously. Anxious to have an international hearing for his ideas, Kepler not only sent copies to specific astronomers, but he sent along a pair of the books with an emissary to Italy. Apparently the ambassador was already working his way back from Rome when he realized that he had done nothing about Kepler's request. Looking around for a suitable recipient, he handed both copies over to the professor of mathematics in Padua, a man of some local reputation but certainly unknown north of the Alps since he had not yet published anything. The Italian wrote a hasty reply, indicating that he, too, had supported Copernicus privately. Kepler mentioned the reply in a letter to his former teacher, Maestlin, bemusedly reporting that there was an Italian astronomer with the same first name as last name: Galileo Galilei. The young Kepler promptly wrote back to Galileo, urging him to stand forth openly in favour of the Copernican doctrine. There the correspondence temporarily ended, not to be resumed until both had established brilliant reputations as Copernicans, Kepler as imperial mathematician and author of the Astronomia nova, and Galileo as the discoverer of satellites of Jupiter and the mountains on the moon.

Through both their scientific work and their polemics, these two men brought a dynamic new life to the perception of the Copernican theory. When Galileo and Kepler began to hammer out a new terrestrial and celestial physics, they both realized that they must also counter the scriptural arguments before the Copernican system would be widely accepted. Kepler, in the introduction to his Astronomia nova argued that the Scriptures were written in everyday language for common understanding, and should not be taken literally. Galileo, at much greater length in a letter to the Grand Dutchess Christina, argued similarly. He said: "I think in the first place that it is very pious to say and prudent to affirm that the Holy Bible can never speak untruth-whenever its true meaning is understood. But I believe that nobody will deny that it is often very abstruse, and may say things which are quite different from what its bare words signify. Hence in expounding the Bible if one were always to confine oneself to the unadorned grammatical meaning, one might fall into error."

The entry of such an accomplished polemicist as Galileo into the territory of the theologians was cause for alarm in ecclesiastical circles. It was not so much the particulars of the heliocentric cosmology as the fear of the argument that the Book of Nature might provide a more direct route to Truth than the Book of Scripture. Physical reality as differentiated from theological truth was a scarcely perceived distinction, and therefore an obvious place to draw the battle lines was on the interpretation of Copernicus' doctrine. Heliocentrism was not at fault per se, but it was essential, in the eyes of the churchmen, for Copernicus' work to be perceived as hypothetical and not a physical reality. The powerful Cardinal Bellarmine accepted Me position of Osiander's preface when he wrote in 1615 in a famous letter to Foscarini: "It seems to me that your Reverence and Signor Galileo would act prudently were you to content yourselves with speaking hypothetically and not absolutely, as I have always believed Copernicus spoke."

Unfortunately from the churchmen's viewpoint, Copernicus himself was annoyingly vague concerning whether or not he believed in the reality of his system. Furthermore, by this time Kepler had conspicuously announced the true authorship of the anonymous introduction to De revolutionibus, so it could no longer be maintained that Copernicus necessarily subscribed to the view given there. Hence, from the vantage point of the Holy Congregation of Rome, the most expeditious course was to suspend Copernicus' book until the appropriate adjustments could be made in the text. Decree XIV of the Holy Congregation of the Index, issued 5 March 1616, reads in part: "Whereas it has also come to the knowledge of this Congregation, that the Pythagorean doctrine-which is false and altogether opposed to Holy Scripture-of the motion of the earth, and the quiescence of the sun, which is also taught by Nicholas Copernicus in De revolutionibus orbium coelestium, and by Diego di Zuniga in (his book on) Job, is now being spread abroad and accepted by many,. . . therefore, in order that this opinion may not insinuate itself any further to the prejudice of Catholic truth, the Holy Congregation has decreed that the said Nicholas Copernicus, De Revolutionibus orbium, and Diego di Zuniga, on Job, be suspended until they be corrected."

The expression "donec corrigatur" - "until corrected"-belonged to the standard vocabulary of the Inquisition, but in only one case did the Holy Congregation ever announce specific corrections. That unique treatment was reserved for Copernicus' De revolutionibus. The report made to the Congregation of the Index on the proposed censorship of the Copernicus' book De revolutionibus still survives, although it is little known and has not yet been published in English. Unlike the final decree announcing the corrections, the report gives the background reasons for the action. It was probably written by Bonifacio Caetani, one of the Cardinals who had persuaded the pope to label the heliocentric doctrine as false rather than heretical. In a nutshell, it says there are three basic considerations. First, astronomy is important to the church for calendarial reasons, and Copernicus' book must be preserved for its observations and for the restoration of astronomy. Second, to remove the heliocentrism would not be a correction, but the total destruction of his system. Finally, it is possible to proceed by a middle way without compromising the Holy Writ by emending certain passages, and now I quote: "If certain of Copernicus' passages on the motion of the earth are not hypothetical, make them hypothetical; then they will not be against either the truth or the Holy Writ. On the contrary, in a certain sense, they will be in agreement with them, on account of the false nature of suppositions, which the study of astronomy is accustomed to use as its special right."

Decree XXI, finally issued in 1620, announced about a dozen corrections. They have been reprinted in various places, among them Augustus de Morgan's Budget of Pardoxes, which in the 1915 edition and 1954 reprint includes an English translation. Let me here mention only a few of them. Concerning the eighth chapter of book 1, the Decree stated: "This whole chapter can be deleted because it admittedly deals with the truth of the earth's motion, while it refutes the ancient reasons for proving its immobility. If, however, it would please the most illustrious fathers that this chapter be emended, Copernicus may be made to seem to speak always problematically and from opinion... [This] would better satisfy students, since the sequence and arrangement of the books would remain intact."

I have now personally examined nearly every surviving sixteenth-century copy of Copernicus' book, and I have found only a single example of where chapter 8 has been totally excised-the 1566 edition in the public library in Cremona.

Generally the censor provided a substitute text for the phrase, sentence, or sentences deleted. A particularly characteristic substitution occurs for the title of chapter 11, originally "On the demonstration of the three-fold motion of the earth," and changed to read "On the hypothesis of the three-fold motion of the earth and its demonstration." Immediately before this, at the end of chapter 10, is another interesting change. Copernicus describes how the retrograde motion of Jupiter is smaller than Mars', and Saturn's is still smaller than Jupiter's because each is successively farther from the sun. Finally, the stars show no discernable annual motion because they are so far away-"So great, without any question, is the divine handiwork of the Almighty Creator." The Holy Congregation, apparently wishing to avoid an apparent Divine imprimatur on the system, deleted this stirring finale to Copernicus' glorious cosmological chapter.

My Copernican census, undertaken during the past decade, now for the first time provides evidence concerning the effectiveness of the censorship. Because the instructions of 1620 were so specific, it is possible to determine rather accurately whether or not a copy was censored. Of about 400 copies now in Europe, 33 were censored, or about I in 12. From a careful analysis of the provenances, it is possible to reconstruct where the majority of these books were in 1620, and thus I conclude that about 60% of the copies in Italy were censored, and relatively few elsewhere. For example, in France, where many copies were in Jesuit libraries, there was comparatively little censorship; apparently the Jesuits considered the Index primarily a Dominican concern! My census revealed a quite unexpected and initially puzzling situation with respect to Spain and Portugal, where none of the copies are censored. In Madrid I turned up the uncensored copy once owned by Juan de Pineda, a Spanish theologian active in the early 1600s; subsequent research showed him to be the editor of the Spanish version of the Index. Pineda's version explicitly prohibited Rheticus' Narratio prima as reprinted in the 1566 Basel edition of Copernicus' book, and indeed, Pineda had sliced these offending pages from his copy. Pineda could hardly have been unaware of Decree XXI, but his Seville Index specified no changes in the De revolutionibus text itself, and apparently neither Pineda nor any others on the Iberian peninsula deleted any part of the Copernican treatise.

Even in Italy the physical process of the censorship was highly variable. In some cases ink or paper paste-overs completely obliterated the original text. In others, such as Galileo's own copy, the deletions hardly concealed anything, and in a few, such as a copy in the Lincei Academy, the corrections almost seem to emphasize Copernicus' original statements. In fact, when Kepler's Epitome of Copernican Astronomy was placed on the Index in 1619, a Venetian correspondent assured him that his work would be read all the more attentively in Italy. More than anything else, the suspension and correction of De revolutionibus probably merely gave Copernicus' ideas abundant free publicity.

Galileo's trial and its inhumanity, coming a dozen years after the censorship, was considerably more consequential. It cast a damper on scientific inquiry throughout Catholic Europe and destroyed creative science in Italy for several generations. But the censorship itself had little effect in maintaining the primacy of Scripture over Nature as the path to truth about our physical world. It was as fruitless as King Canute commanding the tides to stop.

There are, for better or worse, still many people who claim the Bible as a scientific textbook and who wish to regard scientific theories as hypothetical and thus fictional. In this matter I side with Galileo, who quoted Cardinal Baronius in saying that the Bible teaches how to go to heaven, not how the heavens go. In the generation following Galileo, Milton would write

Heav'n
Is as the Book of God before thee set
Wherein to read his wondrous works...
... whether Heavn move or Earth
Imports not ..

Without committing himself on the cosmology, Milton was already conceding the legitimacy of the Book of Nature. Within another generation came Milton's countryman Isaac Newton, who "feigned no hypotheses." Newton read the Book of Nature to establish a physical coherency and thus a persuasive justification for the heliocentric blueprint of the Universe. Censorship, even scientific censorship, remains in our world today, and it may well be far more effective and insidious than in the seventeeth century. Copernicus' book was finally removed from the Index in 1835, but long before, by the time of Newton, the censorship of De revolutionibus had run its course ineffectively.

Presented at the American Astronomical Society, Historical Division, San Francisco, 15 January 1980. A longer version is being prepared for the An nali dell'Istituto e Museo di Storia della Scienza di Firenze.