By any criterion Chomsky's achievement is vast. As the guiding spirit of the cognitive revolution, he has been instrumental in changing our view not just of language but of human nature. He has tamed the infinite complexity of language, and in doing so has given us a new appreciation of what we owe to the hand of nature and what we owe to the environment. He has done it through insight, through fanatical hard work and by devoting his efforts to problems rather than mysteries. Problems come in different forms: some, like I-language, are amenable to theoretical discussion; others, like politics, require not so much a theory as the dispassionate application of common sense in the scrutiny and presentation of the facts. Solving any of them requires dedication.

By contrast, there are areas such as the evolution of language that, because of the impossibility of getting relevant evidence, seem to be mysteries. That language is the result of evolution seems to be undeniable; that we can say anything interesting about how it evolved seems dubious. Human emotions are not beyond understanding: good novelists have insights into the human condition that evade the science of psychology. Free will, the ultimate mystery, seems not to be amenable to treatment by either novelists or philosophers or psychologists.