"As I look through the structure of the words and the structure of the sentences, it just becomes clear that they don't have recursion. If recursion is what Chomsky and Mark Hauser and Tecumseh Fitch have called 'the essential property of language', the essential building block—in fact they've gone so far as to claim that that might be all there really is to human language that makes it different from other kinds of systems—then, the fact that recursion is absent in a language — Pirahã — means that this language is fundamentally different from their predictions."