This is a sentence from an article in The New Yorker.
One day, Prince demanded that he see the crew member’s portfolio.
My question is about the form of the verb 'see' here. Why not 'sees' or 'saw'? What is the grammar behind this construction?
English Language Learners Stack Exchange is a question and answer site for speakers of other languages learning English. It only takes a minute to sign up.Sign up to join this community
 One day, Prince demanded [that he see the crew member’s portfolio].
Your example  is known as the subjunctive mandative, a special kind of construction with a subordinate content clause headed by a plain form verb - in this case "see". Like imperative clauses, mandatives invoke the concept of compliance: Prince demanded compliance. The mandative subjunctive is the 'standard' form in all varieties of English for conveying such meaning using a subordinate content clause.
 Prince demands [that he sees the crew member’s portfolio].
 One day, Prince demanded [that he saw the crew member’s portfolio].
It is also possible for the mandative to have the form of an ordinary declarative content clause - sometimes called the 'covert mandative'. Covert mandatives contain a present tense verb, as in  or else a backshifted preterite, as in . The covert type is comparatively rare, and in AmE particularly is generally considered unacceptable.