How does language work, and how do we learn to speak? Why do languages change over time, and why do they have so many quirks and irregularities? In this original and totally entertaining book written in the same engaging style that illuminated his bestselling classics, The Language Instinct and How the Mind Works, Seven Pinker explores the profound mysteries of language. By picking a deceptively simple phenomenon--regular and irregular verbs--Pinker connects an astonishing array of topics in the sciences and the humanities: the history of languages; the theories of Noam Chomosky and his critics; the attempts to create language using computer simulations of neural networks; what there is to learn from children's grammatical "mistakes"; the latest techniques in identifying genes and imaging the brain; and major ideas in the history of Western philosophy. He makes sense of all this with the help of a single, powerful idea: that language comprises a mental dictionary of memorized words and a mental grammer of creative rules. His theory extends beyond language and offers insight in the very nature of the human mind.