Wh-movement

What causes wh-movement is an important question raised by the preceding analysis Chomsky (1998, 1999, 2001) proposes that the process that leads wh-expressions to spec-CP is a [EPP] feature. He claims that, just as T in finite clauses has a [EPP] feature that requires it to be extended into a TP projection with a subject as its specifier, C in wh-questions has a [EPP] feature that requires it to be extended into a CP projection with a wh-expression as its specifier.

The previous section's EPP analysis of wh-movement has fascinating implications for the syntax of multiple wh-questions containing two or more independent wh-expressions. (For a study of the semantic features of such queries, see Dayal 2002.) One important grammatical feature of such inquiries in English is that only one of the wh-expressions can be preposed — as an echo question demonstrates.

When an object moves, it carries 'just enough material for convergence' with it. The phrase "just enough material for convergence" effectively means "just enough material to assure that the resulting structure is grammatical," because a convergent derivation produces a grammatical structure that can be assigned an acceptable semantic and phonetic representation.

As a result, the relative clause in brackets in the, It's difficult to locate people [you can trust] will require merging a relative pronoun such as who as the object of the verb trust, resulting in the relative clause having the structure illustrated below at the point where the complementiser is merged with its TP complement

[C thatWH, EPP] [TP you [T can] [VP [V trust] who]]

The [WH, EPP] features of the complementiser that will attract the relative pronoun who to become the specifier of that and are thereby deleted (along with the trace copy of the moved pronoun who).