''An Inspector Calls'', first produced in 1946 when society was undergoing sweeping transformations, has recently enjoyed an enormously successful revival. While holding its audience with the gripping tension of a detective thriller, it is also a philosophical play about social conscience and the crumbling of middle class values. ''Time and the Conways'' and ''I Have Been Here Before'' belong to Priestley's 'time'plays, in which he explores the idea of precognition and pits fate against free will. ''The Linden Tree'' also challenges preconceived ideas of history when Professor Linden comes into conflict with his family about how life should be lived after the war.