In 30 short minutes, Dr. Keller gives one of the best talks on the title question: How could a good God allow pain and suffering? He gives a philosophical answer, and perhaps more importantly for some, discusses the personal aspect, emphasizing the two Christian resources of the cross and the resurrection. In the talk, Keller draws on many sources, from C. S. Lewis to Albert Camus. The included Q&A session is also very good. Keller's an excellent and personable speaker and I hope his message gives you something to think about.