Colorless green ideas sleep furiously was composed by Noam Chomsky in his 1957 book Syntactic Structures as an example of a sentence that is grammatically well-formed, but semantically nonsensical. The sentence was originally used in his 1955 thesis The Logical Structure of Linguistic Theory and in his 1956 paper "Three Models for the Description of Language".[1]: 116 There is no obvious understandable meaning that can be derived from it, which demonstrates the distinction between syntax and semantics, and the idea that a syntactically well-formed sentence is not guaranteed to also be semantically well-formed. As an example of a category mistake, it was intended to show the inadequacy of certain probabilistic models of grammar, and the need for more structured models.
- ^ Chomsky, Noam (September 1956). "Three Models for the Description of Language" (PDF). IRE Transactions on Information Theory. 2 (3): 113–124. doi:10.1109/TIT.1956.1056813. S2CID 19519474. Archived (PDF) from the original on 2016-03-07.