MIT linguist Pinker builds on his previous successes (How the Mind Works; The Language Instinct) with another book explaining how we learn and deploy word, phrase and utterance. Some linguists (notably Noam Chomsky) have argued that everything in speech comes from hidden, hard-wired rules. Others (notably some computer scientists) claim that we learn language by association, picking up raw data first. Pinker argues that our brains exhibit both kinds of thought, and that we can see them both in English verbs: rule application ("combination") governs regular verbs, memory ("lookup") handles irregulars. The interplay of the two characterizes all language, perhaps all thought. Each of Pinker's 10 chapters takes up a different field of research, but all 10 concern regular and irregular forms of words. Pinker shows what scientists learn from children's speech errors (My brother got sick and pukeded); from survey questions (What do you call more than one wug?); from similar rules in varying languages (English, German and Arapesh); from theoretical models and their failings and from brain disorders like jargon anomia (whose victims use complex sentences, but say things like "nose cone" when they mean "phone call"). Sometimes Pinker explains linguists' current consensus; at other times, he makes a case for his own theoretical school. His previous books have been accused of excessive ambition; here he largely sticks to his own fields. The result, with its crisp prose and neat analogies, makes required reading for anyone interested in cognition and language.