The author of Darkness at Noon must be listened to attentively, no matter what he may choose to write upon. Arthur Koestler is a very clever, knowledgeable and inventive man, and The Act of Creation is very clever too, and full of information, and quite wonderfully inventive in the use of words. Koestler’s theory of the creative act is set out in Book One as a special theory comprehended within a General Theory that occupies Book Two. Koestler is far too intelligent a man not to realize that his account of creative activity is full of difficulties, but though he mentions the contexts in which some of them arise, he does not direct attention to them explicitly or make any attempt to work them out. Koestler declares that at each level of the hierarchy ‘homologous’ principles operate, with the consequence that any phenomenon at one level must have its homologue or formal counterpart at each other level.