TASK DEFINITION: You will be given a trivia clue, and the category it belongs to. You should answer with the best answer that belongs in the category and is described by the clue. For simplicity, answers should be in all lower cased letters.
PROBLEM: Category: POLITICAL PHILOSOPHY 
Clue: The subtitle of this influential 1762 treatise is "Principes du droit politique" ("Principles of Political Right")

SOLUTION: the social contract

PROBLEM: Category: U.S. HISTORY 
Clue: The day affer the 15th Amendment took effect, Thomas Peterson became the 1st Afr. American to do this under its provisions

SOLUTION: vote

PROBLEM: Category: INTERNATIONAL PLAYWRIGHTS 
Clue: (Jimmy of the Clue Crew reports from the Yale Repertory Theatre)  During apartheid, this man chose to premiere several of his plays, including "A Place with the Pigs", here at Yale

SOLUTION:
athol fugard