The Act of Creation is divided into two books. In the first book, Koestler proposes a global theory of creative activity encompassing humour, scientific inquiry, and art. Koestler's fundamental idea is that any creative act is a
bisociation (not mere association) of two (or more) apparently incompatible frames of thought. Employing a spatial metaphor, Koestler calls such frames of thought
matrices: "any ability, habit, or skill, any pattern of ordered behaviour governed by a 'code' of fixed rules." Koestler argues that the diverse forms of human creativity all correspond to variations of his model of bisociation. In jokes and humour, the audience is led to expect a certain outcome compatible with a particular matrix (e.g. the narrative storyline); a punch line, however, replaces the original matrix with an alternative to comic effect. The structure of a joke, then, is essentially that of
bait-and-switch. In scientific inquiry, the two matrices are fused into a new larger synthesis. The recognition that two previously disconnected matrices are compatible generates the experience of
eureka. Finally, in the arts and in ritual, the two matrices are held in juxtaposition to one another. Observing art is a process of experiencing this juxtaposition, with both matrices sustained. According to Koestler, many bisociative creative breakthroughs occur after a period of intense conscious effort directed at the creative goal or problem, in a period of relaxation when rational thought is abandoned, like during dreams and trances. Koestler affirms that all creatures have the capacity for creative activity, frequently suppressed by the automatic routines of thought and behaviour that dominate their lives. ==Book Two: Habit and Originality==