<P> In Aspects Chomsky writes that "linguistic theory is mentalistic, since it is concerned with discovering a mental reality underlying actual behavior ." With this mentalist interpretation of linguistic theory, Chomsky elevated linguistics to a field that is part of a broader theory of human mind, i.e. the cognitive sciences . According to Chomsky, a human child's mind is equipped with a "language acquisition device" formed by inborn mental properties called "linguistic universals" which eventually constructs a mental theory of the child's mother tongue . The linguist's main object of inquiry, as Chomsky sees it, is this underlying psychological reality of language . Instead of making catalogs and summaries of linguistic behavioral data demonstrated on the surface (i.e. behaviorism), a Chomskyan linguist should be interested in using "introspective data" to ascertain the properties of a deeper mental system . </P> <P> The mentalist approach to linguistics proposed by Chomsky is also different from an investigation of the neurophysiological mechanisms underlying language . It is about abstractly determining the properties and functions of such mechanisms . </P> <P> In Aspects, Chomsky summarized his proposed structure of a grammar in the following way: "A grammar contains a syntactic component, a semantic component and a phonological component...The syntactic component consists of a base and a transformational component . The base, in turn, consists of a categorial subcomponent and a lexicon . The base generates deep structures . A deep structure enters the semantic component and receives a semantic interpretation; it is mapped by transformational rules into a surface structure, which is then given a phonetic interpretation by the rules of the phonological component ." In this grammar model, syntax is given a prominent, generative role, whereas phonology and semantics are assigned secondary, interpretive roles . This theory of grammar would later come to be known as the "Standard Theory" (ST). </P> <P> The base in the syntactic component functions as follows: In the first step, a simple set of phrase structure rules generate tree diagrams (sometimes called Phrase Markers) consisting of nodes and branches, but with empty terminal nodes; these are called "pre-lexical structures". In the second step, the empty terminal nodes are filled with complex symbols consisting of morphemes accompanied by syntactic and semantic features, supplied from the lexicon via lexical insertion rules . The resulting tree diagram is called a "deep structure". </P>

Aspects of the theory of syntax by noam chomsky