“You mustn’t be afraid to dream a little bigger, darling,” is the advice that one character gives another in Christopher Nolan’s Inception. With this film, the director of The Prestige and The Dark Knight proves once again that no other big-budget filmmaker has dreams quite as large as his. Part existential spy film, part science-fiction epic and part heist movie, Inception is by far the boldest and best film in a disappointing Hollywood summer season.