  Secondly, Chomsky argued — and here we see his first invocation of the famous ‘poverty of the stimulus’ argument, to be  discussed in more detail in §2.2 below — it is unclear  that conditioning could even in principle give rise to a set of dispositions rich enough to generate the full range of a person's  linguistic behavior. In order, for example, to acquire the  appropriate set of dispositions concerning the word car, one would have to be trained on vast numbers of sentences containing that word: one would have to hear car in object position and  car in subject position; car modified by adjectives and car unmodified; car embedded in opaque contexts (e.g. in propositional attitude ascriptions) and car used  transparently; and so on. But the ‘primary linguistic  data,’ usually referred to as the ‘pld’  and comprising the set of sentences to which a child is exposed  during language learning (plus any analysis performed by the child on those sentences; see below), simply cannot be assumed to contain  enough of these ‘minimally differing sentences’ to fully  determine a person's dispositions with respect to that word. Instead, Chomsky argued, what determines one's dispositions to use  car is one's knowledge of that word's syntactic and semantic properties (e.g., car is a noun referring to cars), together with one's knowledge of how elements with those properties function  in the language as a whole. So even if language mastery were (in  part) a matter of having dispositions concerning car, the  mechanism of conditioning would be unable to give rise to them. The  training set to which children have access is simply too limited: it  doesn't contain enough of the right sorts of exemplars.