"Taxi Driver," viewed in the wake of the shooting of U.S. Rep. Gabrielle Giffords, unfolds like the keys you need to understand how something so horrible as an assassination happens. It is a profile in isolation, desperation, crisis of self-worth and the corrosive effects of an unhealthy society. You can see the trials of the misfit as he attempts to fit in with others and the deepening despair and feelings of insignificance that follow the failures. You can follow the logic trail to violence as expression of last resort. The arc of the storyline is so perfectly realized that the end feels almost tacked on, a throwaway comment on the attraction of manly, heroic violence that rings false, unless I'm misreading it. Either way, this is a storied and deservedly decorated piece of filmmaking, with brilliant turns by Robert DiNiro and Jodie Foster, and a great American director at or near the height of his powers.