Sometimes, to appreciate how good a film is you have to imagine how bad it could have been. The conventional way of telling a story is beginning-middle-end, cause-effect-remedy, disease-diagnosis-cure. But if Kenneth Lonergan had taken that strict linear approach in crafting Manchester by the Sea, we would have been deprived of the element of discovery that makes it such a powerful film. To put it this way, Lonergan could have opened with the calamitous event that so blights the life of Lee Chandler (Casey Affleck), and then shown the breakup with his wife, Randi (Michelle Williams); his efforts to lose himself in menial work as a handyman/custodian in Boston; the death of his brother, Joe (Kyle Chandler), and Lee's return to Manchester; the discovery that Joe has made him guardian of Joe's son, Patrick (Lucas Hedges), and the subsequent attempts to arrange his life around that fact. But by postponing the revelation of the terrible event in Lee's life, placing it in a flashback, Lonergan makes it what it has to be: the very center of the film. We want to know what is troubling Lee, why he's so blocked emotionally, and Lonergan makes us wait for the answer, to speculate what it might be. When the revelation comes that he accidentally killed his small children, it probably fulfills what many of us had guessed it might be, so it doesn't come as a brutal surprise but as an elucidation. To put it at the start of the film, including Lee's aborted attempt at suicide, would have turned the film into a sentimental slog toward redemption. But by first showing us the ways in which Lee has responded by hiding away or lashing out at comforters or the curious -- by putting the middle before the beginning, the effect before the cause -- Lonergan focuses on Lee's continuing everyday pain, not on the enormity of what caused it. And then there's the ending: poignant, inconclusive, but at least somewhat hopeful. A conventional ending that provided balm for the pain, a cure for the disease, would have been phony. We may want the film to end with Lee finding some consolation like that of new fatherhood with Patrick, a rapprochement with Randi, even some kind of successful therapy or -- like Elise (Gretchen Mol), Joe's druggie ex-wife and Patrick's strayed mother -- submission into religious faith, but we would be satisfying our desire for a tidy narrative, not Lee's deep needs. Lonergan handles the traditional religious "cure" brilliantly, showing Patrick's discomfort at the evangelical piety of Elise and her new husband, Jeffrey (Matthew Broderick), and his complaint to Lee that Jeffrey is "Christian." Lee reminds him that they're Christians too -- "Catholics are Christians" -- ironically widening the gulf between Patrick and his mother and her husband. Lee's Catholicism is steeped in guilt, an emotion he knows too well and cannot imagine a life without. The strength of a film like Manchester by the Sea lies in its acknowledgment that life is too shaggy, bristly, and spiky to be neatly wrapped up with cures and fixes for whatever ails it.