Book excerpt: In this paper,(1) I will restrict the term ""linguistic theory"" to systems of hypotheses concerning the general features of human language put forth in an attempt to account for a certain range of linguistic phenomena. I will not be concerned with systems of terminology or methods of investigation (analytic procedures). The central fact to which any significant linguistic theory must address itself is this: a mature speaker can produce a new sentence of his language on the appropriate occasion, and other speakers can understand it immediately, though it is equally new to them. Most of our li.