The Sleepwalkers. Arthur Koestler. Hutchinsons. 25/-.

sub-titled “A history of man’s changing vision of the universe”, the main part of this book is concerned with the revolution in cosmology associated mostly with the names of Copernicus, Kepler, Galileo and Newton. In his introduction, Koestler defines his aim as being to inquire into the psychology of scientific discovery and incidentally to debunk legends attaching to it. This is needed. An honest biography of a scientist, especially one alive during the last century or so, is something almost non-existent and Koestler rightly sees that the marble pedestal approach, long abandoned in other branches of historiography, must go here too. So long as science’s official histories insist on pictures of perfection, the complementary unofficial pictures of absent-minded professors, evil geniuses and cold destroyers of spiritual values, etc., must likewise persist.

Secondly, Koestler wants to inquire into the division of science and religion at what he believes to be its source in the conflict of Galileo with the Church. Thirdly, he expresses himself concerned about the cold war between the sciences and humanities.

Copernicus, in Koestler’s account, appears as a reluctant dragon but an unattractive one, timid, conventional, pedantic and dull, conservative in a revolutionary age and attempting nothing outside astronomy in an age of brilliant all-rounders—an innovator in spite of himself. Koestler shows that instead of marking a break with Aristotelian physics, Copernicus’ idea was a last attempt to reconcile it with the facts. Moreover, Copernicus never made any astronomical observations of his own, and performed his calculations on out-of-date observations which had, in any case, been falsified to fit the theories of other people. Koestler concludes that only an obsessionally conservative mind would have bothered to attack the problem in the way that Copernicus did.

This is perhaps too severe. The most natural way of interpreting the apparent motion of the fixed stars and the sun is by the revolution of spheres around the earth. This was the basis of the Aristotlelian dogma. It is then quite natural to seek to explain the motions of the planets on the basis of circular motions. Given the idea of a sun-centred universe, it would again automatically be the first thing to have been tried. Koestler throughout the book makes a great point of the complexities of Copernicus’ theory, exaggerating somewhat their importance.

The longest and best part of the book concerns the lives and discoveries of Kepler, who found the elliptical form of the planetary orbits a necessary preliminary to Newton’s discovery of gravitation, and Tycho Brahe, who supplied the necessary accurate observational data. The thought of such early scientists as Paracelsus, Gilbert and Descartes makes us realise “the fallacy of the belief that at some point between the Renaissance and the Enlightenment, man shook off the superstitions of medieval religion, like a puppy getting out of the water, and started on the bright new road of Science”. For in these minds we find modern intuitions hopelessly mixed with mediaeval idea. In Kepler this contradiction is sharper than in anyone because of the very exactness, and exactingness, of his purely scientific achievements.

A delightful thing about Kepler is that he has left a vivid account of the progress of his work so that one is able to follow it step by step. Unlike Newton he did not knock away the scaffolding. He provides almost unique material for anyone interested in the psychology of discovery. Mr. Koestler has done a magnificent job in following and setting out Kepler’s amazing, agonising train of thought—how he uses erroneous data, makes mistakes in arithmetic, the mistakes cancel out, realises his errors and tries to explain why they cancelled and is again mistaken, how he draw wrong conclusions, corrects them, then later forgets what he has done and uses his earlier false ideas, and how this erratic, but still rational process is all the time mixed up with ideas and ways of thought which are fantastic in the true sense of the word.