It lays out Koestler's attempt to develop an elaborate general theory of human creativity. From describing and comparing many different examples of invention and discovery, Koestler concludes that they all share a common pattern which he terms "bisociation"--A blending of elements drawn from of two previously unrelated matrices of thought into a new matrix of meaning by way of a process involving comparison, abstraction and categorization, analogies and metaphors. He regards many different mental phenomena based on comparison (such as analogies, metaphors, parables, allegories, jokes, identification, role-playing, acting, personification, anthropomorphism etc.), as special cases of "bisociation".