What makes us decide an actor is “good” or “bad”? Why are we obsessed with Hollywood celebrities? How much are we acting in our everyday life? What would have happened if Marlon Brando had never landed the role of Stanley Kowalksi in “Streetcar Named Desire?” These are some of the questions film critic and author David Thomson ponders in his new book “Why Acting Matters.” He says we love to watch acting because it inspires us to better understand and envision our own lives — and that we can’t but help to be actors ourselves. David Thomson joins Diane to discuss the art of pretending on screen, on stage and in everyday life.