When we say that Jones has the language L, we now mean that Jones’s language faculty is in the state L, which we identify with a generative procedure embedded in performance systems. To distinguish this concept of language from others, let us refer to it as "I-language", where I is to suggest "internal", "individual", and "intensional". The concept of language is internal, in that it deals with an inner state of Jones's mind/brain, independent of other elements in the world. It is individual in that it deals with Jones, and with language communities only derivatively, as groups of people with similar I-languages. It is intensional in the technical sense that the I-language is a function specified in intension, not extension: its extention is the set of SD (what we might call the "structure" of the I-language).
- Chomsky (1995), Pag. 15