Copernicus: Platonist Astronomer-Philosopher
Cosmic Order, the Movement of the Earth, and the Scientific Revolution
Table Of Contents
- About the author
- About the book
- This eBook can be cited
- Table of contents
- A Note on Primary Texts and Translations
- List of Figures
- Part One. The Motion of the Earth: A Solution to the Problems of Astronomy
- Chapter I. Uniform Circular Motion of Celestial Bodies
- Chapter II. Celestial Spheres and the Problem of the Equant
- Chapter III. A Stationary Earth and the Forma Mundi Problem
- Chapter IV. The Consensus of Many Centuries: The Motion of the Earth is Inconceivable
- Chapter V. The Politics of Science: The Dedication to the Pope
- Part Two. Argumentation in Favor of The Earth’s Motion
- Chapter VI. The Earth is a Terraquea Sphaera
- Chapter VII. The Postulate of Uniform Circular Motion of Celestial Spheres and Celestial Phenomena
- Chapter VIII. The First Motion of the Earth and the “Optical Argument”
- Chapter IX. The Dialectics and Physics of the Earth’s First Motion
- 1. Copernicus, Ptolemy and the Centrifugal Force Argument
- 2. Copernicus, Ptolemy and Falling Bodies (and Clouds)
- 3. Copernicus’ Positive Arguments in Favor of the Earth’s Rotation
- Chapter X. The Second Motion of the Earth and its Position in the “World Machine”
- Part Three. Copernicus in Context
- Chapter XI. Astronomy before Copernicus
- 1. Three Approaches to Studying the Heavens in the Middle Ages
- 2. Vienna School of Astronomy, Renewal and Criticism of Ptolemy’s Almagest and Homocentric Astronomy
- Chapter XII. How did Copernicus Become a Copernican?
- 1. A General Outline of Copernicus’ Education
- 2. Copernicus’ Encounter with the Problems of Astronomy
- 3. Platonism as a Common Denominator
- 4. Copernicus’ Platonism, the Problems of Existing Astronomy and his Solutions
- Chapter XIII. The Platonist Astronomer-Philosopher and the Scientific Revolution
- 1. Copernicus in Comparison with Averroists
- 2. Copernicus’ Revolutionary Reformation of Ptolemaic Astronomy
← 10 | 11 → INTRODUCTION
To us inhabitants of the earth it seems as though the earth stands still, while the stars make a full circle around it every twenty-four hours. The stars appearing in the east in the evening are closer to the west in early morning; the sun rising in the east in the morning, moves across the sky towards the mountains and sets behind them in the evening; the moon follows a similar path.
Little wonder then that we cannot shake the habit of talking about the ways of the stars in such a manner; of talking about the sun as though it were a tiny lantern that indeed travelled across the skies. Yet, upon closer reflection, reason prevails once again over perception and teaches us: the stars are immeasurably distant; but how are they to circle the earth in twenty-four hours, given this tremendous distance?
On account of such remoteness, it may flash across everyone’s mind that there must be other explanations for the ways of the stars. And it is as follows: The earth, this gigantic orb soaring free in the heavens, makes a full rotation about its axis in twenty-four hours, leading us, its inhabitants, to believe that the stars revolve around us. This appearance is not deceptive in itself, for in the morning the sun is indeed in the east, and in the evening it truly appears where it is seen, in the west. However, the cause of such a change is not the sun but the earth revolving from east to west. No one in their right mind can have any doubt about it today; for aside from the stars’ remoteness, the science of the stars has furnished proofs that can in no way be faulted.
Dr. Gregorij Pečjak, Stoletna pratika dvajsetega stoletja, 1901–2000, pp. 51–2.
← 11 | 12 → Within the horizon of the world we live in – that defined by our senses – the earth is at rest. We cannot see or sense its movement; we feel it firmly fixed beneath our feet. On the other hand, we can observe the sun rise every clear morning and set in the evening, just as we can notice the stars rise in the east every evening and then move towards the west. Within the horizon of man’s existence, this appearance is a truth as clear as sunlight. Even from the practical point of view, the earth appears motionless to us. For maritime transport and other purposes of orientation it is completely sufficient to have star charts and other maps based on the assumption that the earth is the stationary centre of the universe.
Yet despite the undetectability of its motion, and very limited practical use of this fact, we know that the earth moves. As the heirs of the Scientific Revolution, whose results have definitively affirmed that the earth is one of the wandering stars, we assume our planet’s rotation about its axis and revolution around the sun to be completely self-evident and irrefutable. Not the slightest doubt can topple the evidence furnished by “the science of the stars” as supported by the sound theories of mathematical physics of modern astronomy and cosmology. Moreover, on the basis of verified scientific theories, we also know today that the earth travels around the sun along an elliptical orbit and that its motion is caused by the force of gravity. In an age when science has become man’s second nature, the assertion that the earth stands still sounds rather unusual, if not downright insane.
However it was not always so. Until the period known as the Scientific Revolution or, until the sixteenth and particularly seventeenth centuries (and even later), a vast majority condemned as foolish anyone who would claim the opposite: that the earth moves. In all great civilizations, including the Greek, Arab and Christian ones, the earth as the stationary centre of the universe was – with negligible exceptions – the foundation of everyday life, religion and philosophy. The notion of a moving earth was inconceivable and incomprehensible to the inhabitants of Greek poleis in the fifth century BC, Arab merchants in the ninth century AD, and Christian monks in the twelfth century AD alike. Its movement could not, and still cannot, be perceived in any Lebenswelt. Quite to the contrary: people of all ages, cultures and religions could always clearly see that the earth stands still while celestial bodies travel around it. The deities of all major religions, too, have created a world with the motionless earth at its centre, while philosophers and scholars of every worldview and orientation have been, ← 12 | 13 → regardless of their customary and irreconcilable differences, unanimous: The earth is the solid ground beneath our feet.
The questions I answer in this book are fairly simple: Why did Nicolaus Copernicus (1473–1543) assert, first in the unpublished Commentariolus (ca. 1510) and later in the impressive De revolutionibus (1543), that the earth moves while the sun is at rest in the centre of the universe? Why did he think that astronomy of his time was in the need of a reform based on the concept of terrestrial motion? How did he introduce this concept into astronomical discourse, and what argumentative strategy did he use to do so? And finally, what does his assertion mean for the history of human, particularly scientific and philosophical, thought?
Copernicus’ name has long been a synonym for the radical revolution in astronomy that took place in the sixteenth and seventeenth centuries; many historians of science have even identified the year of 1543 as the beginning of new scientific thought not only in astronomy but in natural science as a whole. In his work The Copernican Revolution, Thomas Kuhn extended the scope of the revolution even further.1 In his view, Copernicus brought about change not only in mathematical astronomy and science but philosophy in the broadest sense.
Before Copernicus, the earth was the fixed centre around which a host of other celestial bodies revolved. He proposed to improve the accuracy and simplicity of astronomical theories by attributing to the sun a number of astronomical functions that had previously been attributed to the earth, and one century later, the sun, at least in astronomy, replaced the earth as the centre of planetary motions while the earth lost its singular astronomical status and became one of the moving planets. Many subsequent astronomical achievements depend on this shift; for this reason, this radical change in the fundamental concepts of astronomy is known as the Copernican Revolution.
The aforementioned change, however, says Kuhn, is only the first of the revolution’s meanings. The publication of De revolutionibus was soon followed by other radical changes in human understanding of nature. Many innovations that culminated one hundred and fifty years later in Isaac Newton’s conception of the universe were unintentional by-products of Copernicus’ astronomy. Although the sole reason that Copernicus proposed the earth’s motion was to improve the techniques used in predicting the astronomical positions of the celestial bodies, his suggestion only raised new problems for other strains of science. Until these were solved, his concept of the universe remained incommensurable with those of ← 13 | 14 → other scientists. The reconciliation of these sciences with Copernicus’ theory was an important cause of the intellectual ferment in the seventeenth century which we know today as the Scientific Revolution. The Scientific Revolution not only reconciled Copernicus’ astronomy and physics, but assigned to science the role, which it has since played in the development of Western society and its thought.
Yet, according to Kuhn, even this does not completely exhaust the meanings of the Copernican Revolution. Copernicus lived and worked in an age permeated with rapid changes in political, economic and intellectual life that formed the basis for modern European and American civilization. His planetary theory and associated concept of a heliocentric universe vastly contributed to the transition from medieval to modern Western society, because they appeared to affect human relations to the universe and God. Copernicus’ theory, which started as a strictly technical, mathematical revision of classical astronomy, became the focus of momentous discussions in religion, philosophy and social theory that determined the substance of human thought for two centuries after the discovery of America. Those who did not believe that their terrestrial home was no more than a planet blindly orbiting one of a myriad of stars sought to determine their place in the cosmic scheme differently from their predecessors who saw the earth as a singular and pivotal centre of God’s creation. “Copernicus’ revolution” therefore also contributed to the change in values of the Western European civilization.
Nevertheless, does the fact that it was Copernicus who put the earth in motion, thus making it focal to seventeenth century thought, eo ipso mean that he himself was also part of the Copernican Revolution and the Scientific Revolution? Was he himself already subject to a radical conceptual “revolution which implies a radical intellectual ‘mutation’”? Did he himself already “destroy one world and […] replace it by another,” or did he himself reshape the “framework of our intellect,” “restate and […] reform its concepts,” “evolve a new approach to Being, a new concept of knowledge, a new concept of science”?2 According to traditional historiography of science, or the “vulgar triumphalist view” as Robert Westman puts it,3 this is most certainly true. The “triumphalists” clearly deemed Copernicus a revolutionary who decisively and completely broke with medieval and ancient philosophic and scientific principles. He overturned the finite cosmos of Aristotle (384–322 BC) and Ptolemy (ca. 90–ca. 168 AD), and replaced it with ← 14 | 15 → the infinite universe of stars. Relying on extensive calculations, he shattered the perfect crystalline spheres which had carried the planets around the earth since ancient times. And finally, he made a bold move of radical simplification and reduced the cumbersome number of epicycles introduced by Ptolemy to predict the planetary positions from eighty (or so) to thirty-four.
However, more careful readings of Copernicus’ work undertaken by historians and philosophers of science after World War II revealed an entirely different and considerably less revolutionary image. Westman highlights the four most important conclusions of the research: although Copernicus’ universe was appreciably bigger in size than that of Ptolemy, it was still finite; although Copernicus regarded the sun as the motionless centre of the planetary motions, he did not place it exactly at the centre of the universe but slightly off it. Furthermore, Copernicus was not a diligent observer: he made about twenty-seven new observations, but none were important for his theory; he did not eliminate the celestial spheres, although he was ambiguous about their true nature; he indeed eliminated several epicycles, but by abolishing the Ptolemaic mechanism called the equant, he also added new ones.4 The conclusions made by historical epistemology during the first decades after World War II can be summarized thus: with Copernicus, the All (to pan, i. e. the Universe or the Whole) had undergone an effective change – but not in all aspects.
In contrast to the image of Copernicus as a hero of the Scientific Revolution, the results of this research reveal the true meaning of his De revolutionibus in terms of the impact his work had on the Copernican Revolution and hence on the whole Scientific Revolution of the seventeenth century. By putting the earth in motion, Copernicus also started the wheels of the Scientific Revolution. The motion of the earth, a concept so utterly inconceivable to Aristotelian natural philosophy, came to dominate the thought of the Scientific Revolution, creating ever new challenges and generating ever new solutions that ultimately culminated in the Newtonian concept of the universe. Although the Scientific Revolution is to a great extent a Copernican Revolution – if we disregard the Copernicanism of Galileo Galilei (1564–1642), Johannes Kepler (1571–1630) and Isaac Newton (1642–1727), we basically disregard the Scientific Revolution itself – Copernicus’ work alone does not represent a revolutionary breakthrough. As Kuhn explains:
The principal difficulties of De revolutionibus and the ones that we may not evade arise rather from the apparent incompatibility between that text ← 15 | 16 → and its role in the development of astronomy. In its consequences the De revolutionibus is undoubtedly a revolutionary work. From it derive a fundamentally new approach to planetary astronomy, the first accurate and simple solution of the problem of the planets, and ultimately, with other fibres added to the pattern, a new cosmology. But to any reader aware of this outcome, the De revolutionibus itself must be a constant puzzle and paradox, for, measured in terms of its consequences, it is a relatively staid, sober, and unrevolutionary work. Most of the essential elements by which we know the Copernican Revolution – easy and accurate computations of planetary position, the abolition of epicycles and eccentrics, the dissolution of the spheres, the sun a star, the infinite expansion of the universe – these and many others are not to be found anywhere in Copernicus’ work. In every respect except the earth’s motion, the De revolutionibus seems more closely akin to the works of ancient and medieval astronomers and cosmologists than to the writings of the succeeding generations who based their work upon Copernicus’ and who made explicit the radical consequences that even its author had not seen in his work.5
According to Kuhn, the true significance of De revolutionibus therefore lies “less in what it says itself than in what it caused others to say.”6 The book caused a revolution that it itself barely foreshadowed. Thus De revolutionibus is “a revolution-making rather than a revolutionary text.”7
Therefore, the significance of Copernicus’ work alone lies not so much in its inherent scientific achievements as it does in its effects on future scholars or, first and foremost, in the destruction of ancient geocentrism and medieval anthropocentrism. Since the time of Copernicus, as Alexandre Koyré states in The Astronomical Revolution, “man has ceased to be the centre of the Universe, and the Cosmos ceased to be regulated around him.”8 Pursuant to Koyré, Copernicus’ work involved “the destruction of a world that everything – science, philosophy, religion – represented as being centered on man, and created for him; the collapse of the hierarchical order […].”9 Nevertheless, the old world’s response was long overdue:
← 16 | 17 → Only at a much later date, when it became evident that this work of Copernicus was not intended for mathematicians alone; when it became clear that the blow to the geocentric and anthropocentric Universe was deadly; when certain of its metaphysical and religious implications were developed in the writings of Giordano Bruno [(1548–1600)], only then did the old world react.10
According to Koyré, the first stage of the astronomical revolution – the destruction of geocentrism and anthropocentrism – was followed by Kepler’s step, in which celestial dynamics replaced the kinematics of circles and spheres used by Copernicus and ancient astronomers. Kepler’s work enabled a partial transcendence of the obsession with circularity and the triumphant entrance of the astronomy of ellipses into the universe. With Giovanni Alfonso Borelli (1608-1679), the unification of celestial and terrestrial physics was finally completed by the abandonment of the circle in favor of the straight line leading to infinity. The ideas of Kepler and Borelli were then further refined by Newton.11
Kuhn’s and Koyré’s basic argument that Copernicus started the work but never brought it to completion may also be expressed in a different, simpler and more eloquent manner: Copernicus was truly a man of the sixteenth century, not the seventeenth. This is already evident from his approach towards his own project. Copernicus never thought of himself as a revolutionary; quite to the contrary. His aim as a genuine Renaissance astronomer was by no means “to reverse the entire science of astronomy,”12 but to restore it by relying on the true, ← 17 | 18 → authentic foundations, principles and postulates of the ancient philosophy and astronomy, which were violated by the predominant Ptolemaic astronomical tradition. However, in order to achieve this goal, he had to sacrifice one of the fundamental premises of the entire astronomy and cosmology of his time – the stationary earth at the centre of the universe. In its stead he introduced into astronomy a new and, by all contemporary articulations of knowledge, absurd concept of a moving earth. But Copernicus did so by harkening back to and rescuing the time-honored, yet forgotten ancient tradition of terrestrial motion. Copernicus was a man of the Renaissance who, in accordance with the spirit of his day, developed the new by rediscovering and renewing (renovatio) the old.13
For the most part, Kuhn and Koyré view Copernicus from the perspective of the Scientific Revolution; they both inquire how significant his work was for the revolution’s achievements. Such a perspective and investigation is, of course, completely legitimate, and we shall deal with them further on in this book. However, before addressing the question of his “revolutionariness,” it is, in order to fully grasp Copernicus’ significance for the Scientific Revolution, first necessary to view him from the perspective of his self-understanding, through his own eyes, and from the perspective of the understanding of his contemporaries, against the background of the state of astronomy and philosophy in the sixteenth century, which itself was also the culmination of a centuries-long development. To put it differently, the true significance of any project, scientific or not, can only be appreciated when set within a sufficiently long as well as adequately studied historical period. Certain theses, emphases and facts can be endowed with true significance and meaning only within a history of long duration.
Historical and epistemological studies performed in the recent decades and even years have revealed a much clearer picture of astronomy, philosophy, and theology of the sixteenth century that facilitates a much more accurate understanding and evaluation of Copernicus’ project then those done by Kuhn and Koyré. For the time being, let me mention only one crucial example. On the basis of Copernicus’ critical account on the state of mind in astronomy in his ← 18 | 19 → dedicatory preface To His Holiness, Pope Paul III. Nicolaus Copernicus’ Preface to his Books On the Revolutions or Preface to De revolutionibus,14 Kuhn derives a thesis in The Copernican Revolution that the Copernican Revolution occurred because the Ptolemaic astronomic paradigm was in a state of crisis. In The Structure of Scientific Revolutions, he then extends his conclusion to the whole of science:
And Copernicus himself wrote in the Preface to the De revolutionibus that the astronomical tradition he inherited had finally created only a monster. By the early sixteenth century an increasing number of Europe’s best astronomers were recognizing that the astronomical paradigm was failing in application to its traditional problems. That recognition was prerequisite to Copernicus’ rejection of the Ptolemaic paradigm and his search for a new one. His famous preface still provides one of the classic descriptions of a crisis state.15
But Kuhn is mistaken. He takes Copernicus both too lightly and too seriously at the same time. Copernicus’ depiction of the “crisis state” in the Preface is not directed entirely against the “Ptolemaic paradigm.” Quite to the contrary: one of the aims of Copernicus’ reform (rather than “rejection”) of the astronomy was to develop one variant of Ptolemaic astronomy. On the other hand the Preface is no more than a rhetorical radicalization and dramatization of some issues known for centuries. But contrary to Kuhn’s belief, no other astronomer before Copernicus recognized that the Ptolemaic astronomical paradigm was “failing.” The biggest question for which I shall try to find an adequate answer is: Why did Copernicus, and nobody before him, all of a sudden find these centuries-old issues so troublesome? What happened that motivated Copernicus to venture into so radical a reform of Ptolemaic astronomy? Why and how did he become a Copernican? Or, as Bernard Goldstein puts it in his very important article “Copernicus and the Origin of his Heliocentric System”: “[w]hat was the question for which heliocentrism was the answer?”16
In very recent years, at least three substantial and very important books (and several important articles), all of them excellent achievements in their own way, addressed more or less explicitly this question. Robert Westman, The Copernican Question: Prognostication, Skepticism, and Celestial Order (2011), asks himself ← 19 | 20 → basically the same question as Goldstein, and looks for the answer, as reveals the subtitle of the book, in astrology.17 According to Robert Westman, Copernicus’ envisioned the reform of astronomy as a defense of the astrology which came under attack by Pico della Mirandola (1463–1494) in his Disputationes adversus astrologiam divinatricem published in 1496. The major issue of Pico’s criticism was the inability of astronomers and astrologers to establish certain, fixed order of planetary spheres. Westman in my opinion poses the right question and rightfully underlines the role of Disputationes as one of Copernicus’ major sources on uncertainty in regard of the arrangement of the cosmos, but I do not believe Copernicus envisioned astronomical reform in order to save astrology. On the other hand, André Goddu, in Copernicus and the Aristotelian Tradition (2010), somehow implies that Copernicus’ project grew out of his Aristotelian background. I think we should rather look in the opposite direction, that is, towards Plato and Platonism. Goddu himself documents Copernicus’ familiarity with works of various Platonists and Plato and even proposes original argument for the influence of Plato’s ideal of dialectic from the Parmenides on Copernicus’ argumentation in Commentariolus, but apart from that he makes little use of the Platonic tradition in explaining the origin and the development of Copernicus’ heliocentrism. This is not the case in Anna De Pace’s excellent Niccolò Copernico e la fondazione del cosmo eliocentrico con testo, traduzione e commentario del Libro I de Le rivoluzioni celesti (2009). De Pace provides new sources and evidence to show, quite convincingly, how much Copernicus owes to Plato and Platonism. I agree with her general interpretation of Copernicus as Platonist, however, I would argue, she does not go far enough. She gives too much importance to some particular issues, such as Copernicus’ Platonist theory of gravity, which in my opinion is not crucially important for him, and underemphasizes others, such as more metaphysical, Pythagorean-Platonic (read: mathematical) concerns with the cosmic order and ideas about the purpose of that order for humankind.
These latter issues are, as I will show, the main factors which not only stimulated Copernicus’ criticism of Ptolemaic astronomy, but even shaped his heliocentric solution. In other words, Copernicus’ Platonism explains all of the fundamental aspects of his project. His Platonism brings unity and coherence to his work and links into a consistent philosophical stance seemingly unrelated issues, such as the equant problem and the problem of the order of the planetary spheres.
← 20 | 21 → Copernicus’ Platonist conceptions also provide historical and contextual background of his achievement, that is, it explains the nature of what I believe to be a genuine Copernican Revolution. By affirming the earth’s motion, and particularly by transposing the argumentation pro et contra earth’s movement from the sphere of natural philosophy to that of mathematical reasoning, Copernicus produced something that he failed to thoroughly consider. Although that gesture eluded more explicit reflection – Galileo Galilei mentions it in passing – it unambiguously opened up a radically new epistemological horizon: a horizon in which mathematical reasoning takes precedence over our reliance on sensory experience or appearances and establishes itself as decisive criterion of truth. Here, in my opinion, lies the very essence of Copernicus’ own Copernican Revolution and his greatest contribution to the Scientific Revolution.
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- Publication date
- 2014 (May)
- Renaissance wissenschaftliche Revolution mittelalterliche Astronomie antike Astronomie Platonism Commentariolus
- Frankfurt am Main, Berlin, Bern, Bruxelles, New York, Oxford, Wien, 2014. 451 pp., 22 b/w fig.