Derivational vs. constraint-based views

The central tasks of current linguistic theory are twofold. The first task is to explain how children are able to acquire grammatical competence even though they do not receive explicit instruction or have limited access to the data. This task is thus to account for the gap between children's knowledge of language and the apparent lack of substantive input for language, also known as Plato's problem. For example, assume that Korean speakers may hear both of the following Korean sentences including a relative clause:

From these two examples, speakers may infer that a subject from a matrix clause as well as from an embedded clause can be relativized. However, note that Korean speakers may not utter sentences like the following:

Note that just like those in (1), the sentence in (2) also relativizes the subject of the embedded clause, but Korean speakers would not utter such a sentence. The question that follows is then how and why the language users, with no explicit instruction, can avoid generating such an unacceptable sentence.

The next and related task is to explain syntactic competence in language. Native speakers have the ability to combine structures to create simple as well as complex sentences.