Free The Sleepwalkers by Arthur Koestler

poetic tissue is preserved in vitro , its volatile spirit condensed and frozen. The result is the Aristotelian model of the universe.
    The Ionians had prised the world-oyster open, the Pythagoreans had set the earth-ball adrift in it, the Atomists dissolved its boundaries in the infinite. Aristotle closed the lid again with a bang, shoved the earth back into the world's centre, and deprived it of motion.
    I
shall describe the model first in its broad outline, and fill in the
details later.
    The immobile earth is surrounded, as in the earlier cosmologies, by nine concentric, transparent spheres, enclosing each other like the skins of an onion (see Fig. A, p. 46). The innermost skin is the sphere of the moon; the two outermost are the sphere of the fixed stars, and beyond that, the sphere of the Prime Mover, who keeps the whole machinery turning: God.
    The God of Aristotle no longer rules the world from the inside, but from the outside. It is the end of the Pythagorean central fire, the hearth of Zeus, as a divine source of cosmic energy; the end of Plato's mystic conception of the anima mundi , of the world as a living animal possessed with a divine soul. Aristotle's God, the Unmoved Mover, who spins the world round from outside it, is the God of abstract theology. Goethe's " Was wär' ein Gott der nur von aussen stiesse " – seems to be aimed directly at him. The removal of God's home from the centre to the periphery automatically transformed the central region, occupied by earth and moon, into that farthest away from Him: the humblest and lowliest of the whole universe. The space enclosed by the sphere of the moon and containing the earth – the "sub-lunary region" – is now considered definitely inferior. 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.
    This splitting-up of the universe into two regions, the one lowly, the other exalted, the one subject to change, the other not, was to become another basic doctrine of mediaeval philosophy and cosmology. It brought a serene, cosmic reassurance to a frightened world by asserting its essential stability and permanence, but without going so far as to pretend that all change was mere illusion, without denying the reality of growth and decline, generation and destruction. It was not a reconciliation of the temporal and the eternal, merely a confrontation of the two; but to be able to take in both in one glance, as it were, was something of a comfort.
    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 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.
    The system had yet another advantage. It was a compromise between two