Language
Language takes pride of place because it is often considered the one faculty that makes humans unique, although we shall consider other candidates in later chapters. In the Chomskyan view of language, moreover, recursion is seen as its most distinguishing feature. As we shall see in the following three chapters, though, this view is undergoing some revision, and there may even be some languages that do not make use of recursive principles. Moreover, closer scrutiny of animal communication suggests greater continuity than a strict Chomskyan or Cartesian perspective might imply. The notion of continuity is buttressed by the argument that language evolved from manual gestures rather than from vocal calls, as I explain in chapter 3.
Even so, language remains vastly more complex than any form of animal communication, and understanding how it evolved, it has been suggested, might be “the hardest problem in science.”1 Language may not always draw on recursive principles, but a main theme of this book is that it nevertheless depends on the recursive nature of nonlinguistic thought. In this view, language is a central ingredient of human thought as an adaptation to social modes of thinking that had evolved independently. This theme is elaborated in parts 2 and 3.