Language is a hallmark of the human species, the flexibility and unbounded expressivity of our linguistic abilities is unique in the biological world. In this book, Morten Christiansen and Nick Chater argue that to understand this astonishing phenomenon, we must consider how language is created: moment by moment, in the generation and understanding of individual utterances, year by year, as new language learners acquire language skills, and generation by generation, as languages change, split, and fuse through the processes of cultural evolution. Christiansen and Chater propose a revolutionary new framework for understanding the evolution, acquisition, and processing of language, offering an integrated theory of how language creation is intertwined across these multiple timescales.