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

by Arthur Koestler

I use this outmoded expression because the term ‘Science’, which has come to replace it in more recent times, does not carry the same rich and universal associations which ‘Natural Philosophy’ carried in the seventeenth century, in the days when Kepler wrote his Harmony of the World and Galileo his Message from the Stars. Those men who created the upheaval which we now call the ‘Scientific Revolution’ called it by a quite different name: the ‘New Philosophy’. The revolution in technology which their discoveries triggered off was an unexpected by-product; their aim was not the conquest of Nature, but the understanding of Nature.

Now this blackout shutter operates not only in the minds of the ‘ignorant and superstitious masses’ as Galileo called them, but is even more strikingly evident in Galileo’s own, and in other geniuses like Aristotle, Ptolemy, or Kepler. It looks as if, while part of their spirit was asking for more light, another part had been crying out for more darkness. The History of Science is a relative newcomer on the scene, and the biographers of its Cromwells and Napoleons are as yet little concerned with psychology; their heroes are mostly represented as reasoning-machines on austere marble pedestals, in a manner long outdated in the mellower branches of historiography – probably on the assumption that in the case of a Philosopher of Nature, unlike that of a statesman or conqueror, character and personality are irrelevant.

The progress of Science is generally regarded as a kind of clean, rational advance along a straight ascending line; in fact it has followed a zigzag course, at times almost more bewildering than the evolution of political thought.

The reader with a scientific education is asked to bear with explanations which might seem an insult to his intelligence. So long as in our educational system a state of cold war is maintained between the Sciences and the Humanities, this predicament cannot be avoided.

His point is that far from being a step-by-step process of rational advance, scientific progress is erratic and often accidental – a messy, disjointed affair in which unreason plays a vital role. It is not science that Koestler is attacking, but the prevailing ‘science-mythography’:

Koestler’s target is the belief that science, uniquely among human activities, is quintessentially rational. It is the belief in the unique rationality of science that is truly irrational.

The makers of the scientific revolution were not heroic fighters against obscurantism, but thinkers who stumbled on truth almost despite themselves. Dismissing the popular notion that ‘science stood for freedom, the Church for oppression of thought’, Koestler presents the makers of the scientific revolution as shifty, at times cowardly figures, referring to them at one point as ‘moral dwarfs’. He is notably hard on Copernicus and Galileo, archetypal figures in the mythology of scientism, contrasting them with the astrologer and mystic Johannes Kepler – the true hero of the book.

But his encounter with communism had taught him that movements supposedly based in science could be as hubristic as religion in claiming to discern a pattern into which all of human experience could be fitted. Even more than the medieval Church, these modern movements had been ready to sacrifice human lives on a vast scale in order to promote an all-encompassing system of belief.

‘The essence and power of that vision lies in its all-embracing, unifying character; it unites religion and science, mathematics and music, medicine and cosmology, body, mind, and spirit in an inspired and luminous synthesis.’ Like their founder, the Pythagoreans were devotees of mathematics who found in numbers and geometrical forms intimations of a hidden order. Koestler had experienced something akin to such a vision when awaiting death in a Spanish prison cell, and there can be no doubt that he regretted the absence of anything like it in modern science.

For him the fundamental shift that occurred as a result of the scientific revolution was not the move from a view of the universe in which everything circles around the Earth to one in which the planet orbits around the Sun. It was the shift from a way of thinking in which physics and a metaphysical interpretation of the purpose of things were inseparably connected to one in which science could do no more than explain the mechanical workings of a material world. The result was ‘the fatal estrangement’ – the modern war of the soul in which the pursuit of knowledge is at odds with the quest for meaning, a conflict from which Koestler suffered throughout his life.

If Koestler exempts Kepler to some degree from the critical view of the founders of modern science that is presented in The Sleepwalkers, one reason is that Kepler continued to hold ...

We can add to our knowledge, but we cannot subtract from it.

It is not easy to see how the whole thing works, but it is the first approach to a mechanical model of the universe. The boat of the sun god is replaced by the wheels of a clockwork. Yet the machinery looks as if it had been dreamed up by a surrealist painter; the punctured fire-wheels are certainly closer to Picasso than to Newton.

The sixth-century scene evokes the image of an orchestra expectantly tuning up, each player absorbed in his own instrument only, deaf to the caterwaulings of the others. Then there is a dramatic silence, the conductor enters the stage, raps three times with his baton, and harmony emerges from the chaos. The maestro is Pythagoras of Samos, whose influence on the ideas, and thereby on the destiny, of the human race was probably greater than that of any single man before or after him.

The essence and power of that vision lies in its all-embracing, unifying character; it unites religion and science, mathematics and music, medicine and cosmology, body, mind, and spirit in an inspired and luminous synthesis.

The Pythagorean discovery that the pitch of a note depends on the length of the string which produces it, and that concordant intervals in the scale are produced by simple numerical ratios (2 : 1 octave, 3 : 2 fifth, 4 : 3 fourth, etc.), was epoch-making: it was the first successful reduction of quality to quantity, the first step towards the mathematization of human experience – and therefore the beginning of Science.

The twentieth-century European regards with justified misgivings the ‘reduction’ of the world around him, of his experiences and emotions, into a set of abstract formulae, deprived of colour, warmth, meaning, and value. To the Pythagoreans, on the contrary, the mathematization of experience meant not an impoverishment, but an enrichment.

Numbers are eternal while everything else is perishable; they are of the nature not of matter, but of mind; they permit mental operations of the most surprising and delightful kind without reference to the coarse external world of the senses – which is how the divine mind must be supposed to operate. The ecstatic contemplation of geometrical forms and mathematical laws is therefore the most effective means of purging the soul of earthly passion, and the principal link between man and divinity.

The line connecting music with numbers became the axis of the Pythagorean system. This axis was then extended in both directions: towards the stars on one side, the body and soul of man on the other. The bearings, on which the axis and the whole system turned, were the basic concepts of armonia: harmony, and katharsis: purge, purification.

It all went to show that Reality could be reduced to number-series and number-ratios, if only the rules of the game were known.

Numbers were not thrown into the world at random; they arranged themselves into balanced patterns, like the shapes of crystals and the concordant intervals of the scale, according to the universal laws of harmony.

I can easily draw the diagonal of a square, but I cannot express its length in numbers – I cannot count the number of dots it contains. The point-to-point correspondence between arithmetic and geometry has broken down – and with it the universe of number-shapes. It is said that the Pythagoreans kept the discovery of irrational numbers – they called them arrhe¯tos, unspeakable – a secret, and that Hippasos, the disciple who let the scandal leak out, was put to death.

In the words of a modern scholar. ‘Pythagoras is the founder of European culture in the Western Mediterranean sphere.’12 Plato and Aristotle, Euclid and Archimedes, are landmarks on the road; but Pythagoras stands at the point of departure, where it is decided which direction the road will take.

The interactions of climate, race, and spirit, the directional influence of outstanding individuals on the course of History, are so obscure that no predictions are possible even in reverse; all ‘if’ statements about the past are as dubious as prophecies of the future are.

The next, revolutionary step was taken by a pupil of Pythagoras, Philolaus, the first philosopher to attribute motion to our globe. The earth became airborne.

In the centre of his roundabout, Philolaus placed the ‘watch-tower of Zeus’, also called ‘the Hearth of the Universe’ or the ‘central fire’. But this ‘central fire’ is not to be confused with the sun. It could never be seen; for the inhabited part of the earth – Greece and its neighbours – was always turned away from it, as the dark side of the moon is always turned away from the earth. Moreover, between the earth and the central fire Philolaus inserted an invisible planet: the antichthon or counter-earth. Its function was, apparently, to protect the antipodes from being scorched by the central fire. The ancient belief that the far-western regions of the earth, beyond the straits of Gibraltar, are shrouded in eternal twilight2 was now explained by the shadow which the counter-earth threw on those parts. But it is also possible – as Aristotle contemptuously remarks – that the counter-earth was invented merely to bring the number of moving things in the universe up to ten, the sacred number of the Pythagoreans.3 Around the central fire, then, revolved in concentric orbits these nine bodies: the antichton innermost, then the earth, the moon, the sun, and the five planets; then came the sphere carrying all the fixed stars. Beyond this outer shell there was a wall of fiery ether, enclosing the world from all sides.

In spite of its poetic oddities, the system of Philolaus opened up a new cosmic perspective. It broke away from the geocentric tradition – the sturdy conviction that this earth occupies the centre of the Universe, from which, massive and immobile, it never budges an inch. But it was also a landmark in another direction. It separated neatly two phenomena which had previously been mixed up: the succession of day and night, that is, the diurnal rotation of the sky as a whole; and the annual motions of the seven wandering planets.

Accordingly, Venus at times appeared as Phosphoros the ‘morning star’, rising with the sun in her wake, at other times as Hesperos the ‘evening star’ at the sun’s tail; Pythagoras seems to have been the first to recognize that they were one and the same planet.

Once more, in the rear-view mirror, Herakleides’ solution of the puzzle seems simple enough. If Venus moved in an irregular manner relative to the earth, the supposed centre of her orbit, yet danced attendance to the sun, then she obviously was attached to the sun, and not to the earth: she was a satellite of the sun. And since Mercury behaved in the same manner, both inner planets must revolve round the sun – and with the sun round the earth, like a wheel turning on a wheel.

The treatise in which Aristarchus proclaimed that the sun, not the earth, was the centre of our world around which all planets revolve – this crowning achievement of Pythagorean cosmology, which Copernicus was to rediscover seventeen centuries later – is lost. But fortunately, we have the testimony of no smaller authorities than Archimedes and Plutarch, among others; and the fact that Aristarchus taught the heliocentric system is unanimously accepted by the ancient sources and modern scholars.

Thus Aristarchus of Samos had carried the development which started with Pythagoras and was continued by Philolaus and Herakleides, to its logical conclusion: the sun-centred universe. But here the development comes to an abrupt end. Aristarchus had no disciples and found no followers.12 For nearly two millennia the heliocentric system was forgotten – or, shall one say, repressed from consciousness? – until an obscure canon in Varmia, a remote outpost in Christendom, picked up the thread where the Samian had left off.

From Aristarchus there is, logically, only one step to Copernicus; from Hippocrates, only a step to Paracelsus; from Archimedes, only a step to Galileo. And yet the continuity was broken for a time-span nearly as long as that from the beginning of the Christian era to our day. Looking back at the road along which human science travelled, one has the image of a destroyed bridge with rafters jutting out from both sides; and in between, nothing.

Men think it divine merely because they do not understand it. But if they called everything divine which they do not understand, why, there would be no end of divine things!’

Plato is equally hostile to the Pythagoreans’ first and favourite branch of science. ‘The teachers of harmony,’ he lets Socrates complain, ‘compare the sounds and consonances which are heard only, and their labour, like that of the astronomers, is vain’.3 None of this was probably meant to be taken quite literally, but it was – by that extremist school of Neoplatonism which dominated Western philosophy for several centuries, and stifled all progress in science – until, in fact, Aristotle was rediscovered and interest in nature revived.

Plato and Aristotle should rather be called twin-stars with a single centre of gravity, which circle round each other and alternate in casting their light on the generations that succeed them.

They both founded ‘schools’ of a new kind: the first Academy and the first Lyceum, which survived for centuries as organized institutions, and transformed the founders’ once fluid ideas into rigid ideologies, Aristotle’s hypotheses into dogmas, Plato’s visions into theology. Then again, they were truly twin-stars, born to complement each other; Plato the mystic, Aristotle the logician; Plato the belittler of natural science, Aristotle the observer of dolphins and whales; Plato, the spinner of allegorical yarns, Aristotle the dialectician and casuist; Plato, vague and ambiguous, Aristotle precise and pedantic. Lastly – for this catalogue could be continued forever – they evolved systems of philosophy which, though different and even opposed in detail, taken jointly seemed to provide a complete answer to the predicament of their time.

Plato’s Utopia is more terrifying than Orwell’s 1984 because Plato desires to happen what Orwell fears might happen. ‘That Plato’s Republic should have been admired, on its political side, by decent people, is perhaps the most astonishing example of literary snobbery in all history,’ remarked Bertrand Russell.

Aristotle’s politics move along less extreme, but essentially similar lines. He criticizes some of Plato’s most provocative formulations, but not only does he regard slavery as the natural basis of the social order – ‘the slave is totally devoid of any faculty of reasoning’;6 he also deplores the existence of a ‘middle’ class of free artisans and professional men, because their superficial resemblance to the rulers brings discredit on the latter.

For the time being, let us retain this essential clue to Plato’s cosmology: his fear of change, his contempt and loathing for the concepts of evolution and mutability. It will reverberate all through the Middle Ages, together with its concomitant yearning for a world of eternal, changeless perfection:

This ‘mutation phobia’ seems to be mainly responsible for the repellent aspects of Platonism. The Pythagorean synthesis of religion and science, of the mystical and empirical approach is now in shambles.

this is not an expression of humility – neither of the humility of the mystic seeker for God, nor the humility of reason acknowledging its limits; it is the half-frightened, half-arrogant philosophy of the genius of a doomed aristocracy and a bankrupt civilization. When reality becomes unbearable, the mind must withdraw from it and create a world of artificial perfection. Plato’s world of pure Ideas and Forms, which alone is to be considered as real, whereas the world of nature which we perceive is merely its cheap Woolworth copy, is a flight into delusion.

Accordingly, the task of the mathematicians was now to design a system which would reduce the apparent irregularities in the motions of the planets to regular motions in perfectly regular circles. This task kept them busy for the next two thousand years. With his poetic and innocent demand, Plato laid a curse on astronomy, whose effects were to last till the beginning of the seventeenth century, when Kepler proved that planets move in oval, and not circular orbits. There is perhaps no other example in the history of thought of such dogged, obsessional persistence in error, as the circular fallacy which bedevilled astronomy for two millennia.

The space enclosed by the sphere of the moon and containing the earth – the ‘sub-lunary region’ – is now considered definitely non-U. To this region, and to this region alone, are the horrors of Change, of mutability confined. Beyond the sphere of the moon, the heavens are eternal and unalterable.

The division was made intellectually more satisfactory and easier to grasp, by assigning to the two parts of the universe different raw materials and different motions. In the sub-lunary region, all matter consisted of various combinations of the four elements, earth, water, air, and fire, which themselves were combinations of two pairs of opposites, hot and cold, dry and wet. The nature of these elements requires that they move in straight lines: earth downward, fire upward, air and water horizontally. The atmosphere fills the whole sub-lunary sphere, though its upper reaches consist not of proper air, but of a substance which, if set in motion, will burn and produce comets and meteors. The four elements are constantly being transformed one into the other, and therein lies the essence of all change. But if we go beyond the moon’s sphere, nothing changes, and none of the four terrestrial elements is present. The heavenly bodies consist of a different, pure, and immutable ‘fifth element’, which becomes the purer the farther away from the earth. The natural motion of the fifth element, as opposed to the four earthly elements, is circular, because the sphere is the only perfect form, and circular motion is the only perfect motion. Circular motion has no beginning and no end; it returns into itself and goes on forever: it is motion without change.

However, even if European philosophy were only a series of footnotes to Plato, and even though Aristotle had a millennial stranglehold on physics and astronomy, their influence, when all is said, depended not so much on the originality of their teaching, as on a process of natural selection in the evolution of ideas. Out of a number of ideological mutations, a given society will select that philosophy which it unconsciously feels to be best suited for its need.

It was an extremely ingenious system – and completely mad, even by contemporary standards; as shown by the fact that in spite of Aristotle’s enormous prestige, it was quickly forgotten and buried. Yet it was only the first of several equally ingenious and equally mad systems which astronomers created out of their tortured brains, in obedience to Plato’s post-hypnotic suggestion that all heavenly motion must be circular motion centred round the earth.

By the time the Ptolemaic system was perfected, the seven passengers, sun, moon, and five planets, needed a machinery of not less than thirty-nine wheels to move through the sky; the outermost wheel, which carried the fixed stars, made the number an even forty.

It was a monumental and depressing tapestry, the product of tired philosophy and decadent science. But nothing else turned up to replace it for nearly a millennium and a half. Ptolemy’s Almagest,4 remained the Bible of astronomy until the beginning of the seventeenth century.

Here, then, is evidence that to the very end of the antique world, the teaching of Herakleides and Aristarchus was well remembered; that a truth, once found, can be hidden away, buried under the surface, but not undone. And yet the Ptolemaic earth-centred universe, ignoring the specific role of the sun, held the monopoly in scientific thought for fifteen centuries. Is there an explanation for this remarkable paradox?

Apart from this bit of academic gossip in Plutarch, there is no mention in any of the sources of religious intolerance towards science in the Hellenistic Age.