Arthur Koestler's The Sleepwalkers is, the subtitle says, "a history of man's changing vision of the Universe'. The thesis which this history illustrates, we are told, is that science and religion are essentially partners, sharing mystic intuition as their common source. Admittedly, science and religion are now divided, but this division is merely the outcome of some historical events — Galileo's quarrel with the Church of Rome and the ensuing misunderstandings — which could have been avoided; it is high time now to reunite science and faith, so as to save Man from (nuclear) self-destruction. The meat of the volume consists of two essays, one on Kepler, one on Galileo. The former is sympathetic towards its hero and was well received, the latter is critical of its hero and was frowned upon. Prima facie, at least, public opinion was rather apologetic.