  On Chomsky's view, the language faculty contains innate knowledge of  various linguistic rules, constraints and principles; this innate  knowledge constitutes the ‘initial state’ of the language faculty. In interaction with one's experiences of language during  childhood — that is, with one's exposure to what Chomsky calls  the ‘primary linguistic data’ or  ‘pld’ (see §2.1) — it gives rise to a new body of linguistic knowledge, namely, knowledge of a specific  language (like Chinese or English). This ‘attained’ or  ‘final’ state of the language faculty constitutes one's  ‘linguistic competence’ and includes knowledge of the  grammar of one's language. This knowledge, according to Chomsky, is  essential to our ability to speak and understand a language  (although, of course, it is not sufficient for this ability: much  additional knowledge is brought to bear in ‘linguistic  performance,’ that is, actual language   use).[1] 