Syntactic Structures is an influential work in linguistics by American linguist Noam Chomsky, originally published in 1957. It is an elaboration of his teacher Zellig Harris's model of transformational generative grammar. A short monograph of about a hundred pages, Chomsky's presentation is recognized as one of the most significant studies of the 20th century. It contains the now-famous sentence "Colorless green ideas sleep furiously", which Chomsky offered as an example of a grammatically correct sentence that has no discernible meaning. Thus, Chomsky argued for the independence of syntax (the study of sentence structures) from semantics (the study of meaning). Based on lecture notes he had prepared for his students at the Massachusetts Institute of Technology, Chomsky's first book presented contemporary developments in early generative grammar. The approach to syntax is fully formal (based on symbols and rules). At its base, Chomsky uses phrase structure rules, which break down sentences into smaller parts. These are combined with a new kind of rules which Chomsky called "transformations". This procedure gives rise to different sentence structures. Reiterating notions introduced to linguistics by the Danish linguist Louis Hjelmslev, Chomsky stated that this limited set of rules "generates" all and only the grammatical sentences of a given language, which are infinite in number. It was later interpreted that this way of study valued language's innate place in the mind over language as learned behavior, although such ideas are not explicitly stated in the book. Hjelmslev and other European linguists, in contrast, had considered the generative calculus as perfectly non-psychological. Written when Chomsky was still an unknown scholar, Syntactic Structures had a major impact on the study of knowledge, mind and mental processes, becoming an influential work in the formation of the field of cognitive science. It also significantly influenced research on computers and the brain. The importance of Syntactic Structures lies in Chomsky’s persuasion for a biological perspective on language at a time when it was unusual, and in the context of formal linguistics where it was unexpected. The book led to Chomsky eventually becoming recognized as one of the founders of what is now known as sociobiology. Another reason for the fame of Syntactic Structures was that Hjelmslev died in 1965, after which generative grammarians were not clear about the origin of the theory. Some specialists have questioned Chomsky's theory, believing it is wrong to describe language as an ideal system. They also say