Extended projection principle


The extended projection principle is a linguistic hypothesis about subjects. It was proposed by Noam Chomsky as an addendum to the projection principle. The basic idea of the EPP is that clauses must contain a noun phrase or determiner phrase in the subject position.

Details

Most verbs require meaningful subjects—for example, "kick" in "Tom kicked the ball" takes the subject "Tom". However, other verbs do not require meaningful subjects—for example, one can say "it rains" but not "the sky rains". The EPP states that regardless of whether the main predicate assigns a meaningful theta role to a subject, a subject must be present syntactically. As a result, verbs which do not assign external theta roles will appear with subjects that are either dummy pronouns, or ones which have been moved into subject position from a lower position.
Examples which have been proposed to be the result of expletive subject insertion in accordance with the EPP:
  1. It seemed that John would never calm down.
  2. It frequently in Quebec.
  3. There seems to be a problem with the radiator.
Notice that in all of these the overt subject has no referential reading.
In languages that allow pro-drop, the empty category pro can fulfill the requirement of the EPP.
McCloskey proposed that there is one group of languages that lacks the EPP: the VSO languages, which appear not only to lack expletives, but also to lack movement operations triggered by the EPP.