Years ago I read Arthur Koestler’s The Sleepwalkers: A History of Man’s Changing Vision of the Universe, and, stopping by a local used book store, happened upon a copy, and bought it. Now I am slowly rereading it nearly fifty years after I first read it. It’s still a fascinating account, whatever one makes of Koestler’s reliability as an historian.
However, to get to the point. When we get to the early years of Christian dominance in Europe, a period of history which Koestler calls the “Dark Interlude,” we come to what he calls “The Age of Double-Think” (pp. 102 ff.). What is interesting about it is the way that the Christian mind, at this point, was split in two. Throughout this period, although the heliocentric universe had already been widely considered by Greek scientists, and, in fact, it was generally known, even to medieval scholars, that the sun had some influence on the orbits of the planets, the general Christian vision of the universe was geocentric. And so, as Koestler points out, while astronomers like Ptolemy created a celestial geometry, based on the Platonic dogma that motion in the heavens goes in perfect circles, in order to preserve the appearances, the cosmology of the church tended to be a kind of naive Aristotelianism. As Koestler says:
The highly ingenious systems of Aristotle’s fifty-five spheres , or 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. (103)