Big thumbs up from me after catching it on DVD last night. I recommend seeing it twice since the flow of scenes will wreak havoc with your sense of linear time. At least Memento gave you some sensory cues whenever the time machine shifted gears.
No one else plays Purgatory like Sean Penn. He's done so much of it on screen, I think he should get a "time served" sentence at the bar of St. Peter. As in Mystic River, Penn's character, Paul, encapsulates the drama of man in cosmic torment, victimized by forces beyond his control, yet tenaciously unwilling to embrace illusions of resolution or redemption. The theme of "life goes on" recurs in very different contexts, but Paul and the other two protagonists, played by Naomi Watts and Benicio Del Toro, are unified in their refusal of this platitude. Yet in the end, all end up accepting this bitter truth--and it is bitter, not the consoling sentiment we usually intend by it. When tragedy strikes, we have to earn the right to say "Life goes on" and often we must resort to some drastic measure to get there. Anything less is a fraud. 21 Grams would thus make a fascinating addition to a pastoral ministry class on grief and loss.
Jack, played by Del Toro, encapsulates the pitfalls of predestination theology. The line from Scripture about God knowing when a single hair on your head moves pops up a few of times, and I kept shaking my head over the impoverished theological understanding Jack and his pastor received from their Calvinist lineage. The path Jack takes after his "blasphemous" rejection of a deterministic God is essentially Catholic, though deviant in its Pelagian anxieties. He reminds me of Robert De Niro's character in The Mission. But some Promethean act of heroic penance will not cure either man of guilt. It may be a necessary part of the purgatorial process, but it's no bridge to freedom. The greater penance for Jack is returning to his family and "moving on," being a virtuous father and husband to his broken family. Good for a theology class in highlighting the destructive idiocy of hyper-Calvinism found in evangelical and fundamentalist Protestantism.