The Sleepwalkers: A History of Man's Changing Vision of the Universe

by Arthur Koestler

Thus neither ignorance, nor the threats of an imaginary Alexandrian inquisition, can serve to explain why the Greek astronomers, after having discovered the heliocentric system, turned their backs on it.

Their main concern was ‘to save the appearances’. The original meaning of this ominous phrase was that a theory must do justice to the observed phenomena or ‘appearances’; in plain words, that it must agree with the facts. But gradually, the phrase came to mean something different. The astronomer ‘saved’ the phenomena if he succeeded in inventing a hypothesis which resolved the irregular motions of the planets along irregularly shaped orbits into regular motions along circular orbits – regardless whether the hypothesis was true or not, i.e. whether it was physically possible or not. Astronomy, after Aristotle, becomes an abstract sky-geometry, divorced from physical reality. Its principal task is to explain away the scandal of non-circular motions in the sky. It serves a practical purpose as a method for computing tables of the motions of the sun, moon, and planets; but as to the real nature of the universe, it has nothing to say.

Ptolemy also makes it clear why astronomy must renounce all attempts to explain the physical reality behind it: because the heavenly bodies, being of a divine nature, obey laws different from those to be found on earth. No common link exists between the two; therefore we can know nothing about the physics of the skies.

A modicum of split-mindedness and double-think was perhaps not too high a price to pay for allaying the fear of the unknown.

We shall see that, two thousand years later, Johannes Kepler, who cured astronomy of the circular obsession, still hesitated to adopt elliptical orbits, because, he wrote, if the answer were as simple as that, ‘then the problem would already have been solved by Archimedes and Apollonius’.22

During the last few centuries, from about AD 1600 onwards, the progress of science has been continuous and without a break; so we are tempted to extend the curve back into the past and to fall into the mistaken belief that the advance of knowledge has always been a continuous, cumulative process along a road which steadily mounts from the beginnings of civilization to our present dizzy height. This, of course, is not the case. In the sixth century BC, educated men knew that the earth was a sphere; in the sixth century AD, they again thought it was a disc, or resembling in shape the Holy Tabernacle.

Hence the importance of Augustine, who was not only the most influential churchman of the earlier Middle Ages, the chief promoter of the Papacy as a supranational authority, and the originator of the rules of monastic life; but above all the living symbol of continuity between the vanished ancient, and the emerging new civilization.

Most welcome of all was the Neoplatonists’ contempt for all branches of science. From them Augustine ‘derived the conviction, which he transmitted to the succeeding generations of many centuries, that the only type of knowledge to be desired was knowledge of God and the soul, and that no profit was to be had from investigating the realm of Nature’.10

The episode reminds one of the futile denunciation of Aristarchus by Cleanthes; it seems to indicate that even in this period of benightedness, orthodoxy in matters of natural philosophy (as distinct from matters theological) was maintained less by threats than by inner compulsion. At least I am not aware of any recorded instance of a cleric or layman being indicted for heresy in this heresy-ridden age because of his cosmological views.

The Greeks, once they had recognized that the earth was a ball floating in space, had almost at once set that ball in motion; the Middle Ages hastily froze it into immobility at the centre of a rigid cosmic hierarchy. It was not the logic of science, not rational thought that determined the shape of the next development, but a mythological concept which symbolized the needs of the age: the tabernacular universe was succeeded by the universe of the Golden Chain.

The secret of the medieval universe is that it is static, immune against change; that every item in the cosmic inventory has its permanent place and rank assigned to it on a rung of the ladder. It reminds one of the pecking hierarchy in a hen-yard. There is no evolution of biological species, and no social progress; no traffic moves up or down the ladder.

The Babylonian oyster-world, which lay three and four thousand years back, was full of dynamism and imagination compared with this pedantically graded universe, wrapped in cellophane spheres, and kept by God in the deep-freeze locker to hide its eternal shame.

And yet at the same time, cosmology had reverted to a naïve and primitive form of geocentrism – with concentric crystal spheres determining the order of the planets and the accompanying hierarchy of angels. The highly ingenious systems of Aristotle’s fifty-five spheres, of Ptolemy’s forty epicycles were forgotten, and the complex machinery was reduced to ten revolving spheres – a kind of poor man’s Aristotle which had nothing whatever in common with any of the observed motions in the sky. The Alexandrian astronomers had at least tried to save the phenomena; the medieval philosophers disregarded them.

But a complete disregard for reality would make life impossible; and thus the split mind must evolve two different codes of thought for its two separate compartments: one conforming to theory, the other to cope with fact. Up to the end of the first millennium and beyond, the rectangular and oval, tabernacle-inspired maps were piously copied out by the monks; they provided a kind of Sunday idea of the shape of the earth according to the patristic interpretation of Scripture. But coexisting with these was an entirely different kind of map of amazing accuracy, the so-called Portolano charts, for practical use among Mediterranean seamen. The shapes of countries and seas on the two types of maps are as unrelated to each other as the medieval idea of the cosmos and the observed events in the sky.

Medieval life in its typical aspects resembles a compulsive ritual designed to provide protection against the all-pervading potato-blight of sin, guilt, and anguish; yet it was unable to provide it so long as God and Nature, Creator and Creation, Faith and Reason, were split apart.

The purpose of the digressions in this chapter, which seem to have led us so far away from our topic, is to show that the cosmology of a given age is not the result of a unilinear, ‘scientific’ development, but rather the most striking, imaginative symbol of its mentality – the projection of its conflict, prejudices, and specific ways of double-think on to the graceful sky.

Aristotle had not only been a philosopher, but also an encyclopaedist in whom a little of everything could be found; by concentrating on his hard-headed, down-to-earth, non-Platonic elements, the great schoolmen brought back to Europe a whiff of the heroic age of Greece.

Plato maintained that true knowledge could only be obtained intuitively, by the eye of the soul, not of the body; Aristotle had stressed the importance of experience – empiria – as against intuitive aperia:

And yet after these great and hopeful stirrings, the philosophy of nature gradually froze up again in scholastic rigidity – though not entirely this time. The reason for this short splendour and long decline can be summed up in a single phrase: the rediscovery of Aristotle had changed the intellectual climate of Europe by encouraging the study of nature; the concrete teachings of Aristotelian science, elevated into dogmas, paralysed the study of nature. If the schoolmen had merely listened to the cheerful and encouraging timbre in the Stagyrite’s voice, all would have been well; but they made the mistake of taking in what it actually said – and insofar as the physical sciences are concerned, what it said was pure rubbish. Yet for the next three hundred years this rubbish came to be regarded as gospel truth.4

Aristotle divorced science from mathematics. To the modern mind, the most striking fact about medieval science is that it ignores numbers, weight, length, speed, duration, quantity. Instead of proceeding by observation and measurement, as the Pythagoreans did, Aristotle constructed, by that method of a priori reasoning which he so eloquently condemned, a weird system of physics ‘argued from notions and not from facts’. Borrowing his ideas from his favourite science, biology, he attributed to all inanimate objects a purposeful striving toward an end, which is defined by the inherent nature or essence of the thing.

Indeed, Aristotle’s omne quod movetur ab alio movetur – whatever is moved must be moved by another – became the main obstacle to the progress of science in the Middle Ages.

Aristotelian physics is really a pseudo-science, out of which not a single discovery, invention or new insight has come in two thousand years; nor could it ever come – and that was its second profound attraction. It was a static system, describing a static world, in which the natural state of things was to be at rest, or to come to rest at the place where by nature they belonged, unless pushed or dragged;

In the days of Babylon, science and magic, calendar-making and augury, were an indivisible unity. The Ionians separated the wheat from the chaff; they took over Babylonian astronomy, and rejected astrology. But three centuries later, in the spiritual bankruptcy following the Macedonian conquest, ‘astrology fell upon the Hellenistic mind as a new disease falls upon some remote island people’.

The medieval landscape is grown over with the weeds of astrology and alchemy, which invade the ruins of the abandoned sciences. When building started again, they got mixed up in the materials, and it took centuries to clean them out.*

‘In the year 1500 Europe knew less than Archimedes who died in the year 212 BC,’ Whitehead remarks in the opening pages of his classic work.

I shall try to sum up briefly the main obstacles which arrested the progress of science for such an immeasurable time. The first was the splitting up of the world into two spheres, and the mental split which resulted from it. The second was the geocentric dogma, the blind eye turned on the promising line of thought which had started with the Pythagoreans and stopped abruptly with Aristarchus of Samos. The third was the dogma of uniform motion in perfect circles. The fourth was the divorcement of science from mathematics. The fifth was the inability to realize that while a body at rest tended to remain at rest, a body in motion tended to remain in motion.

The main achievement of the first part of the scientific revolution was the removal of these five cardinal obstacles. This was done chiefly by three men: Copernicus, Kepler, and Galileo. After that, the road was open to the Newtonian synthesis; from there on the journey led with rapidly gathering speed to the atomic age. It was the most important turning point in man’s history; and it caused a more radical change in his mode of existence than the acquisition of a third eye or some other biological mutation could have achieved.

This explanation is merely guesswork, but whether true or not, it is in keeping with a curious feature in Canon Koppernigk’s character: his inclination to mystify his contemporaries.

But an error of ten minutes arc amounts to one-third of the apparent width of the full moon in the sky; the Alexandrian astronomers had done better than that. Having made the stars his main business in life, why in heaven’s name did the prosperous Canon never order the instruments which would have made him happier than Pythagoras? Apart from his niggardliness, which had grown worse as the bitter years went by, there existed a deeper, anxious reason for this: Canon Koppernigk was not particularly fond of stargazing. He preferred to rely on the observations of Chaldeans, Greeks, and Arabs – a preference that led to some embarrassing results.

Even in the position he assumed for his basic star, the Spica, which he used as a landmark, was erroneous by about forty minutes arc, more than the width of the moon. As a result of all this, Canon Koppernigk’s life-work seemed to be, for all useful purposes, wasted. From the seafarers’ and stargazers’ point of view, the Copernican planetary tables were only a slight improvement on the earlier Alphonsine tables, and were soon abandoned. And insofar as the theory of the universe is concerned, the Copernican system, bristling with inconsistencies, anomalies, and arbitrary constructions, was equally unsatisfactory, most of all to himself.

There is a type of genius: Bacon and Leonardo, Kepler and Newton, who, as if they were charged with electricity, draw an original spark from any subject they touch, however remote from their proper field; Copernicus was not one of them.

A person was accepted or rejected as a whole; and most people who came into contact with Canon Koppernigk chose the second alternative. Tiedemann Giese, the firm yet tender protector, guide, and spur, is one of the silent heroes of history, who smooth its path but leave no personal mark on it.

This led to the paradoxical result that Canon Koppernigk enjoyed a certain fame, or notoriety, among scholars for some thirty years without publishing anything in print, without teaching at a university or recruiting disciples. It is a unique case in the history of science. The Copernican system spread by evaporation or osmosis, as it were.

The revolutions of thought which shape the basic outlook of an age are not disseminated through text-books – they spread like epidemics, through contamination by invisible agents and innocent germ-carriers, by the most varied form of contact, or simply by breathing the common air.

What we call the Copernican revolution was not made by Canon Koppernigk. His book was not intended to cause a revolution. He knew that much of it was unsound, contrary to evidence, and its basic assumption unprovable. He only half believed in it, in the split-minded manner of the Middle Ages.

Why did Copernicus, after ten years spent in the bubble-bath of Renaissance Italy, adopt this arrogantly obscurantist and anti-humanistic attitude? Why did he hug that apocryphal letter for forty years so close to his heart, like a talisman, make a new translation of it and quote it to the Pope? How could a Renaissance philosopher, a contemporary of Erasmus and Reuchlin, Hutten, and Luther, approve of the preposterous notion that one should not pour the clear water of truth into the muddy wells of the human mind? Why was Copernicus so afraid of the Copernican Revolution? The answer is given in the text: because the pure water would be wasted and the dirt would only get agitated. Here is the core of that anxiety which paralysed his work and crippled his life. The hocus-pocus about the Pythagorean mysteries was a rationalization of his fear of getting sprayed with dirt if he published his theory.

He therefore decided that he should … compose tables with accurate rules but no proofs. In that way, he would provoke no dispute among philosophers … and the Pythagorean principle would be observed that philosophy must be pursued in such a way that its inner secrets are reserved for learned men, trained in mathematics, etc.

Since Osiander knew of Copernicus’ hesitations to publish his manuscript for ‘four times nine years’;63a of his insistence that in the narratio prima his authorship should remain anonymous; of his attempt to publish only his planetary tables without the theory behind them, he must have assumed that Copernicus would agree with his cautious and conciliatory approach, which was merely reiterating the classical doctrine that physics and sky-geometry were matters apart.

Do you wish to know the author of this fiction, which stirs you to such great wrath? Andreas Osiander is named in my copy, in the handwriting of Jerome Schreiber, of Nuremberg. Andreas, who supervised the printing of Copernicus’ work, regarded the Preface, which you declare to be most absurd, as most prudent (as can be inferred from his letter to Copernicus) and placed it on the title page of the book when Copernicus was either already dead or certainly unaware [of what Osiander was doing].

We know that mind has the power to hang on to life and, within limits, to postpone the body’s death. Copernicus’ mind had been wandering, yet there was perhaps just enough determination left to hold out until that moment when his hand could caress the cover of his book.

‘You come to see me at the same age as I myself went to Copernicus. If I had not visited him, none of his works would have seen the light.’103

The main reason for this neglect is the book’s supreme unreadability. It is amusing to note that even the most conscientious modern scholars, when writing about Copernicus, unwittingly betray that they have not read him.

In other words, contrary to popular, and even academic belief, Copernicus did not reduce the number of circles, but increased them (from forty to forty-eight).12 How could this mistaken idea survive for so long, and be repeated by so many eminent authorities? The answer is that very few people, even among professional historians of science, have read Copernicus’ book, because the Copernican system (as opposed to the heliocentric idea) is hardly worth bothering about.

This synopsis of the theory occupies less than twenty pages at the beginning of the book, or about five per cent of the whole. The remaining ninety-five per cent consists of the application of it. And when that is completed, there is hardly anything left of the original doctrine. It has, so to speak, destroyed itself in the process. This may be the reason why no summary, conclusions, or winding-up of any kind is found at the end of the book, although we are repeatedly promised it in the text.

Nor do the planets revolve round the sun – as every schoolboy believes that Copernicus taught. The planets move on epicycles of epicycles, centred not on the sun, but on the centre of the earth’s orbit. There are thus two ‘royal thrones’: the sun, and that imaginary point in space around which the earth moves. The year, that is, the duration of the earth’s complete revolution round the sun, has a decisive influence on the motions of all other planets. In short, the earth appears equal in importance in governing the solar system to the sun itself, and in fact nearly as important as in the Aristotelian or Ptolemaic system.

This was an enormous gain in simplicity and elegance. On the other hand, the shifting of the centre of the universe to a place in the vicinity of the sun entailed an almost equal loss in plausibility. Previously, the universe had possessed a solid hub, the earth, a very solid and tangible hub indeed; now the whole world was hinged on a point in empty space. Moreover, that imaginary point was still defined by the orbit of the earth, and the motions of the whole system still depended on the motions of the earth. Not even the planes of the planetary orbits met in the sun; they oscillated in space, again according to the position of the earth. The Copernican system was not a truly heliocentric one; it was a vacuo-centric system, so to speak.

Ptolemy’s forty crystal wheels-on-wheels had been bad enough, but at least the whole machinery was supported by the earth. Copernicus’ machine had even more wheels, but it was supported neither by the earth, nor by the sun; it had no physical centre.

As Kepler was to remark later on, ‘Copernicus tried to interpret Ptolemy rather than nature’. His absolute reliance not only on the physical dogmata, but on the astronomic observations of the ancients was the main reason for the errors and absurdities of the Copernican system.

Apart from the twenty-seven observations of his own, the entire Copernican system was based on the observational data of Ptolemy, Hipparchus, and other Greek and Arab astronomers, whose statements he had uncritically accepted as Gospel truth, never pausing to consider the possibility of errors committed by careless scribes and translators in those notoriously corrupt texts, nor of mistakes and the doctoring of figures by the ancient observers themselves. When, at last, he realized the unreliability of the data on which he had built, he must have felt that the bottom had fallen out of his system. But by then it was too late to do anything about it.20 Apart from his fear of ridicule, it must have been this realization of its basic unsoundness which made him so reluctant to publish the book. He did believe that the earth really moved. But he could no longer believe that either the earth, or the other planets, really moved in the manner, and along the orbits, which his book assigned to them.

Thus Copernicus’ first impulse to reform the Ptolemaic system originated in his urge to remove a minor blemish from it, a feature which did not strictly conform to conservative Aristotelian principles. He was led to reversing the Ptolemaic system by his desire to preserve it – like the maniac who, pained by a mole on his beloved’s cheek, cut off her head to restore her to perfection. Yet it happened not for the first time in history that a puritan reformer started by attacking a minor imperfection, and ended by realizing that it was a symptom of a deep-rooted and irremediable disease. Ptolemy’s equants were nothing to get excited about, but they were symptomatic of the jarring artificiality of the system.