Meaning in everyday thought and language is constructed at lightning speed. We are not conscious of the staggering complexity of the cognitive operations that drive our simplest behavior. This 1997 book examines a central component of meaning construction: the mappings that link mental spaces. A deep result of the research is that the same principles operate at the highest levels of scientific, artistic, and literary thought, and at the lower levels of elementary understanding and sentence meaning. Some key cognitive operations are analogical mappings, conceptual integration and blending, discourse management, induction and recursion. The analyses are based on a rich array of attested data in ordinary language, humor, action and design, science, and narratives. Phenomena that receive attention include counterfactuals; time, tense, and mood; opacity; metaphor; fictive motion; grammatical constructions; quantification over cognitive domains.