March 1993

Copernicus’ Astronomy and Scientific Argument in the Renaissance.


Thank-you for inviting me here to speak to you about the ‘scientific revolution’. What was so special or ‘revolutionary’ about the scientific revolution? Few would doubt that it provided a significant change, and a genuine increase in our knowledge of the world; but what sort of change, or why such a sudden increase? Were our putative revolutionaries (Copernicus, Tycho, Kepler, Galileo, Torricelli) somehow different from their predecessors in their outlook? Does this explain their contributions and success? Does the scientific revolution represent a special change in the attitudes of thinkers, a shift in mind-set to a ‘scientific perspective’ on knowledge?

In general histories of Europe and the Renaissance, quite simple explanations of the scientific revolution are often allowed to pass, hinged upon claims about heroic figures, manifesting a heroic change in mind-set. One often reads that the revolutionaries, particularly Kepler and Newton, were singular in that they paid the strictest attention to empirical matters, to nature, in their considerations of the world: they would not let a theory go except that it fit with all the facts known, thus leaving no room for error or mystery. Or, like Descartes especially, they strove for a consistency in their thought across all scientific disciplines to ensure that what they presented was plausibly representing the reality of nature. Or, like Galileo, they gave their minds to nature alone, rather than to authority, or what the Bible and religion told them must be so. These sorts of analyses of the scientific revolution, of great men holding up a new standard for the investigation of nature and truth against outmoded approaches, are the norm for many presentations of the scientific revolution in history classes today.

So, the goal of this presentation is to indicate some of the problems with the simple concept of the scientific revolution as a victory of heroic figures and their methods over the dunces among their contemporaries.

Such an account, as voiced by A. D. White and many others, does not do justice to the revolutionaries’ contemporaries, and also doesn’t accurately reflect the characters of the heroes. For when we look closely at the discussions between supposed revolutionaries and reactionaries, we do not see an overwhelming difference in the wit, attention to nature, or sincerity among antagonists.

This becomes evident if we examine one particularly important development: Copernicus’ ideas, and the reception of Copernicus’ astronomy in the 16th Century. It will be made clear how difficult a problem it is to determine what should count as a ‘scientific’ approach when considering the thoughts of scholars in the late Renaissance. For when we look carefully at the character of their ‘scientific’ argument, it becomes hard to find definitive reasons for holding to Copernicus’ theory, and divorcing the authoritarian or religious from the scientific.

Why is Copernicus’ theory obvious to us?

So, we will consider a historical debate over the meaning of Copernicus’ theory, much of which can be found in the first pages of the astronomer Nicholas Copernicus’ great work, “Six Books On the Revolutions of the Heavenly Spheres”. The book put forward the idea in 1543 that the earth revolves around the sun instead of the sun and all other planets similarly revolving around the earth. This was a change in astronomy from a ‘geocentric’ or earth-centered universe to a ‘heliocentric’ one in which the sun, rather than the earth, occupies the central area of the universe.

To understand the problem of comprehending Copernicus’ theory during his time, we need to strip away many preconceptions about the certainty of and the justification for Copernicus’ system. All of us here think that Copernicus’ theory, in partial or general outline, is true; in fact, it is probably obvious to each of us beyond doubt. Nonetheless, it was by no means obvious to everyone educated in these matters in Copernicus’ time, and not simply because their heads were clouded by tradition or by the voices of their teachers. The reason that the Copernican analysis of our planetary system is obvious to us now, and not obvious to them, is largely because of arguments that were formed long after Copernicus’ time.

Consider why you think that the sun is at the center of our solar system. Note that the sun is, for Copernicus, at the center of the universe, and not merely the center of the solar system. He maintained that the planets were kept in their orbits not by momentum and mutual attraction, but rather by nested crystalline spheres, centered near to the sun, that constrained the planets’ motions to specific regions in space.

An account of heliocentrism bringing into play a discussion of force, mass, inertia and attraction, hinted at by Kepler and Descartes, and developed well over 100 years after Copernicus by Newton, explains for most of us why it is true. But this is not the sort of explanation for heliocentrism that you will find in Copernicus’ work. In fact, the physics of the experts of his time presented quite an obstacle to accepting his theory!

Why did Copernicus think his explanation was true, then, and why Galileo, and Descartes, and others before Newton? If we find that the view was not so certainly true in Copernicus’ time as we might have expected it to be, then we have already made progress on this historical problem. The reasons for holding to Copernicus’ theory were compelling for a certain type of person with a certain education and experience. The question is, if there is something special and particularly important about a ‘scientific mind-set’ that leads to knowledge, what is it, and would it lead one to a Copernican view near to Copernicus’ time?

Evidence for and against heliocentrism

What was so special about Copernicus’ position, then, and was it more credible than the geocentric view? There are a good number of important arguments in favor of Copernicus’ position, and they mostly have to do with observational astronomy, the placement of the planets in the night sky. Copernicus explained much more elegantly than before the differences in the rates of motion of different planets across the sky. He similarly explained their tendencies and rates for retrogression, and also why two of the planets, Mercury and Venus, stayed very close to the sun from the point of view of the earth, unlike the other planets. Copernicus’ theory incorporated some very important attractions (see Thomas Kuhn’s book, The Copernican Revolution).

‘Looking at the facts in nature’, then, does provide some support for Copernicus’ view; and all historians agree that such facts were very important in convincing Copernicus of the truth of heliocentrism. But reasonable judgment is not as simple as this would suggest, for many of ‘the facts of nature’ also appeared to count against Copernicus’ hypothesis. It is fair to say that if we were looking at Copernicus’ theory in Copernicus’ time, many of us would doubt the correctness of his claim.

First of all, Copernicus and other astronomers had difficulty explaining the planets’ motions in terms that seemed physically possible. Copernicus’ mechanism for explaining the irregularities of planetary motion was extremely elaborate, difficult, and no less complex than those of his more traditional contemporaries; he shared with the others a theory in which the planets circle the center of the universe describing circles built upon circles. The often discussed doubts about the reality of the Ptolemaic mechanisms transferred directly onto Copernicus’ system.

Copernicus also had to try to explain problems in physics that weren’t problems for those who left the earth at rest at the center of the universe. One such problem is: how do we manage to avoid falling off of a ball of rock and water that spins every day and does a circuit around the sun once a year; and why doesn’t the ball we are on itself fly apart under such conditions? (These problems were solved in a convincing way much later by Newton.)

Despite the weaknesses of his theory, Copernicus felt that he did assert the truth, that the earth went around the sun. Physical arguments against his astronomy give you a taste of how scientists have to negotiate obstacles put up by ‘the facts of nature’ as they are understood in different areas of science. Copernicus saw that he was forced to construct a new physics in order to avoid making his astronomy a physical impossibility; and the physics that he authored, incidentally, would have been no more recognizable to us as a reasonable one than the theory that it replaced. For example, Copernicus felt that he had solved the problem of the earth flying apart by suggesting that it wouldn’t do so because the earth is spherical, and rotation is ‘natural’ to all spheres (Book 1, Chapter 8).

By contrast, the great astronomer of the sixteenth century, Tycho Brahe, attempted to incorporate the advantages of Copernicus’ astronomical system into a view that didn’t present such new physical problems. Tycho, trying to mediate between physical and astronomical intuitions, presented a system in which the earth remained stationary at the center of the spinning universe: the sun orbited it and the rest of the planets orbited the sun. This may begin to show you how difficult it is to decide when a theory such as Copernicus’ becomes believable and where the proper ‘scientific attitude’ might lie.

Realism, and the prefatory sections of Copernicus’ work

We might all agree that what is most important about Copernicus’ theory is not the details of his system. Despite his problems with physics, and the strange mechanisms of circles and epicycles which proved to be quite off the mark, and despite that those of us who are not astronomers tend to base our conviction in the Copernican system on Newtonian reasons, what is important is the shift from ‘geo-‘ to heliocentrism. The special feature of Copernicus’ insight, perhaps, was simply his recognition that the heliocentric system in its rough outlines, if not in its details, must be true, and represent reality–for after all, that is all that survives of Copernicus’ work to the present day. Was such an understanding of the reality of the system that Copernicus put forward, then, the scientifically appropriate conclusion to draw?

To determine this matter, we must delve into the history close to 1543 more carefully, and so, know a little more about Copernicus’ book and astronomical argument in his time. Here, the story gets very interesting and entertaining, for, surprisingly enough, arguments both for and against a realistic approach to Copernicus’ theory can be found in the pages that begin the book, probably much to his dismay!

Copernicus, who was quite old and unwell by the time he had been sufficiently encouraged by his friends that he felt ready to publish his book, entrusted a student of his with the task of taking the manuscript to a publisher in Nuremburg. Copernicus was also quite wary of publishing it, fearing that his views were too radical to be generally accepted. This might well have presented the danger of excommunication, which would also lose for him the role that he had within the Roman Catholic administrative structure as a church canon. It is probably no accident that his student, Rheticus (a Protestant himself), took the manuscript to a press in a protestant area of Europe, since Copernicus’ book might have required a review and imprimatur from the church before being published in Catholic lands. Where one published was a very significant issue in Copernicus’ time as it also is today.

To alleviate his fears of opposition, Copernicus included in the prefatory sections of his work a letter written seven years earlier by Cardinal Schoenberg of Capua, Italy that urged Copernicus to publish his findings. The letter stands authoritatively at the front of the book, subtly suggesting that if anyone thought that the views expressed after it were heretical and wished to challenge Copernicus on them, that person would likely face some significant opposition in the Church. Copernicus’ fears were not idle, for the theory would be noticed in Rome quite quickly, and some participants attempted to bring it up for discussion at the Council of Trent less than ten years after its publication.

The theory, then, was quite contentious, and for this reason the story becomes even more interesting. Rheticus took the manuscript to Nuremburg, and instead of seeing it through the press himself, laid it in the hands of another person, Andreas Osiander, whom he and Copernicus both knew. Osiander, however, took the liberty of adding a page of his own at the beginning: a letter to the reader concerning the contents of the book. A letter quite shocking to Rheticus. Copernicus died just about when the book came out, and we are not sure whether he lived to see it in print, or whether he perished before he published. We do know that Rheticus, when he saw what was done, attempted to blot out Osiander’s contribution by crossing over it in red ink in as many copies of the book as he could. The reason for the shock: Osiander’s letter lays out an instrumentalist conception of Copernicus’ astronomy, denying that it represents the structure of reality, and asserting that it merely presents a useful tool for calculating the positions of the planets; whereas Copernicus’ preface, just two pages later, lays out an argument for a realistic interpretation.

Osiander’s argument is worth a careful look because it indicates just how science has been held in a different sort of light at different times; how beliefs about the sources and certainty of knowledge change over time. For Osiander really represents the voice of tradition and perhaps reason against Copernicus the radical. Osiander takes the instrumentalist position just a little bit into his preface. He suggests that the astronomer predicts the positions of the planets, but cannot hope to discover the true causes or laws underlying their motions. He predicts that many learned men will be indignant about Copernicus’ hypothesis that the earth goes around the sun; but, he continues, “…the author of this work has committed nothing which deserves censure…”

That true laws and real structures cannot be discovered by astronomy, Osiander does not defend straightforwardly, but he goes on in his uninvited preface to illustrate the sort of problem one would have if one interpreted astronomy realistically. Astronomers were unable to explain the variation in brightness of Venus using their strange mechanisms to calculate planetary positions. So we can see that interpreting astronomy realistically would be, as Osiander says, “absurd.” We can see some reasonable basis for his doubts: a reason justifying his claim that “it is clear enough that this subject (astronomy) is completely and simply ignorant of the laws which produce apparently irregular motions.” It is important to note that Osiander’s instrumentalist interpretation of astronomy was mirrored by the approaches to astronomy of a large group of astronomers of Wittenberg, who incorporated Copernicus’ advancements into a variety of other models of the universe in their attempts to simplify the calculating tool.

Hierarchies of knowledge

Osiander’s argument becomes still more interesting, providing further insight into the problems in interpreting the virtues of Copernicus’ claims from the standpoint of the Renaissance thinker. The astronomer puts forward absurd hypotheses that should not be understood realistically; how, then, can we attain certain knowledge, in Osiander’s view? He writes: “Since different hypotheses are sometimes available to explain one and the same motion…an astronomer will prefer to seize on the one which is easiest to grasp; a philosopher will perhaps look more for probability; but neither will grasp or convey anything certain, unless it has been divinely revealed to him.” Here Osiander presents the final piece in the puzzle concerning why he, and many people of his time, did not take astronomy to represent reality for, despite Copernicus’ evidence and assurances, there is also an order of certainty to sources of knowledge to consider. There is a hierarchy of disciplines.

The ordering of disciplines deserves a more careful explanation at this point. Astronomers put forward hypotheses, Osiander argues, but, because different hypotheses might account for the data of the world similarly, astronomers cannot be certain of the truth of their theories. They should instead opt for presenting the picture that seems simplest to them, and easiest to use; and this is what Osiander claims Copernicus has done: the new system, with everything going around the sun, is simpler as astronomy than the Ptolemaic system. But complete certainty, he suggests, is only to be achieved through divine revelation, be it personal, or from the Bible. Osiander’s point is that if astronomical knowledge is only understood properly (that is, instrumentally, as a means for predicting the positions of planets, and not realistically, as a description of the structure of the universe), then one can find nothing objectionable in astronomy.

Why did Osiander conclude that Copernicus’ astronomy should be considered instrumentally? It is perhaps not enough to say that astronomers could always be wrong in their speculations for they could also be right. There is one more piece to this puzzle. There seem to be a variety of distinct sources of knowledge that Osiander has indicated: science, philosophy, and revelation. But what might we do if our best indications from these different sources were to conflict? There has to be some way of adjudicating such a dispute since this sort of conflict had occurred often enough before Copernicus’ time; and a solution that had been proposed long before for scholars was the one that Osiander reflected here in his letter: that science must bow to revelation. Heliocentrism appeared to contradict revelation—the Bible—in many places. In the Psalms, for example, one passage reads “…the world also is established, that it cannot be moved”; and, as Luther said with reference to Copernicus, “This fool wishes to reverse the entire pattern of astronomy; but Scripture tells us that Joshua commanded the sun to stand still, not the earth.” So we have another clear reason for doubting the truth of Copernicus’ theory, and a particularly relevant one, I should think, from the point of view of Andreas Osiander, who was first and foremost an important figure in the Protestant Reformation, and a sometime friend of Luther.

Reason vs. Religion?

Was Osiander simply being less scientific, and more religious than Copernicus in his assessment of the theory? A positive reply to this question may be too simple an answer. Osiander’s instrumentalism is certainly more cautious than Copernicus’ realism. He also has what would appear to be scientifically sound reasons for holding to it; reasons that are augmented when we recall that the Wittenberg astronomers and Tycho created different astronomical systems that preserved many of the advantages of Copernicus’ system, and also consider that instrumentalism has been a respectable scientific position in physics at many times since the 16th century. Does the difference between the scientific and the less scientific lie in the idea of a hierarchy of knowledge? Though Osiander states that we must use the Bible as evidence where astronomical argument cannot provide us with certainty, it may not sit well with us. Is the complete subordination of the word of the Bible one part of the distinction that we are looking for, the respect in which ‘looking to nature’ is relevant to the scientific revolution?

If so, it appears difficult to argue that the complete subordination of the Bible to ‘looking to nature’ is a prevalent feature of Humanistic-scientific argument in Copernicus’ time. No straightforward defense of his astronomy against the claims of this hierarchy of knowledge has been found among Copernicus’ writings. In a book by Rheticus, Treatise on the Motion of the Earth, we can see he argued a place for religion in the hierarchy of knowledge about the world. Rheticus presents what we might expect to be the humanist’s challenge to the authority of the scripture when he writes that the Bible may be inaccurate on matters of physics because it was provided by God not to teach us physics, but to save our souls. “…But as it is clearer than the day that God has left a good deal to our own efforts, so as to stimulate the arts and sciences necessary to life, and the things that pertain to education and the honest use of our minds, we should really follow in these things the thread of nature, by which first principles, reason, and daily experience lead us…” But Rheticus also argues for a clear role for the Bible, for he maintains that on the question of the age of the earth, and whether it is created or eternal, “The physicists…are right in disagreeing with Aristotle…And although Aristotle’s arguments cannot be refuted after the rules and in a philosophical way—and likewise Plato’s [contrary] teachings…—yet because they are against the clear teaching of the Scripture…one must abstain from these tenets, regarding them as impious and sacrilegious.” Rheticus also argues that for rather ordinary physical properties of the universe, as opposed to a matter as ‘metaphysical’ as the beginning of the universe, wherever observation and the philosopher’s argument are not decisive, there the authority of the Bible should be taken as truth. Rheticus maintains that the philosophers should accept the argument that the sphere of the stars around us is surrounded by water, as the book of Genesis makes clear.

Copernicus also brought quasi-religious arguments into play at one point in defending his theory, arguing on the basis of an Aristotelian conception of divinity, that “noble[ness] and divin[ity]” accrue more definitely to immobile things than mobile things, and that thus it is natural that the most noble of all, the heavens and the sun, be immobile, instead of the earth (Book 1, Ch.8). References to the importance of the consonance of physical theory with pre-established religion can also be found in remarks by many leading scientists much further on in history, including such luminaries as Newton and Einstein.


Why did Copernicus believe in heliocentrism? You have been presented with some reasons and many more could be provided. Should others as well-informed as Copernicus and manifesting a ‘scientific attitude’ also have believed his theory at that time? Clearly some such as Rheticus thought so, but it does not appear to be easy to separate the better scientific position from the worse, or the scientific from the non-scientific. For at this early point in the scientific revolution, separations between religion and science, and ‘fact’ hierarchy and authority in knowledge, are much less clear than they might appear from our long perspective.

References and Notes

A good resource for learning about Copernicus’ views and their importance in the history of science is Thomas Kuhn’s The Copernican Revolution (Harvard University Press, 1957). Information on Tycho’s system is also available from Kuhn’s book. Osiander’s preface is considered in more detail by Bruce Wrightsman in The Copernican Achievement (R. Westman, Ed. University of California Press, 1975). More on the Wittenberg astronomers can be found in Owen Gingerich and Robert Westman, The Wittich Connection (Transactions of the American Philosophical Society, Vol. 78, part 7 1988). More on the relation between Copernicans and the churches of Europe can be found in Robert Westman’s article in God and Nature (D. Lindberg and R. Numbers, Eds., University of California Press, 1986). Passages from Copernicus’ book are taken from the translation by A.M. Duncan, Copernicus: On the Revolutions of the Heavenly Spheres (Barnes and Noble, 1976). Rheticus’ book has also been translated into English, with an introduction by G. Hooykaas, under the title G.J. Rheticus’ Treatise on Holy Scripture and the Motion of the Earth (North Holland Publishing Company, 1984).

–Eric Palmer, Ph.D.
University of Utah
Department of Philosophy

Annual Meeting Report

The annual membership meeting of the Humanists of Utah was held Thursday, February 25, 1993 in Eliot Hall of the First Unitarian Church, at 7:30 p.m. Chapter President, Flo Wineriter, opened the meeting with a summary of the significant accomplishments of the Chapter during the past year.

Highlights of his report included the Chapter’s legal standing as a non-profit corporation under Utah State law, a doubling of paid memberships, the initiation of the annual Edwin Wilson Lectures, and the use of $1,600.00 from a Chapter Expansion Grant to give 40 public Libraries a copy of Corliss Lamont’s book, The Philosophy of Humanism, for their circulation department.

The Chapter also received the first annual AHA “Chapter of The Year” award at the Annual Conference in Portland, Oregon.

The Secretary, Wayne Wilson, reported there are 84 dues paying members plus 32 subscribing members and 51 trial members. Our monthly Journal is currently being mailed to 213 addressees.

Our Treasurer, Anna Hoagland, reported a substantial growth in the Chapter’s financial situation. The fiscal year 1992 started with a checking account balance of $956.63 and concluded the year on December 31st with a balance of $2251.18. The Auditing Committee reviewed and verified the accuracy of the Treasurer’s books.

Vice-President Bob Green expressed satisfaction with excellent speakers who have presented at our monthly meetings and said examining the historical development of humanism by outstanding professors will continue. Bob also presented several suggestions for enhancing Chapter activity: those suggestions are reported in depth in a separate article.

Board member Richard Layton declined to run for re-election and was presented an engraved plaque expressing appreciation for his service to the Chapter. Nancy Moore was nominated to replace Richard on the Board. Acting Secretary Wayne Wilson was nominated to serve a full term. By secret ballot the membership voted to elect these two new Board members and maintain the remaining Board Members and Officers for another year.

Revising, clarifying, and updating the Chapter By-Laws created a lively discussion and resulted in an excellent version that should easily guide the present and future membership.

The meeting concluded with an enjoyable social hour of cookies, punch, and coffee prepared by Martha Stewart and Lorille Miller.

— Flo Wineriter