Can architecture inspire people to think and behave differently? David Adjaye is one of the most sought after architects in the world today. Among his many buildings are the Nobel Peace Centre in Oslo, a business school in Moscow, shopping centres in Beirut and Lagos, a children's hospital in Rwanda, a housing project in New York's Harlem and about to open - his biggest project yet - the National Museum of African American History and Culture sitting right on the National Mall in Washington. Has he got it right? What is the test of a good building?