Long Day's Journey into Night: Theme Analysis

The Prison of the Past
The Tyrone family is in a prison of its own making. There have been so many events in the past that have had such a traumatic cumulative effect on them that the shadow of the past extends into the present and the future. It seems as if almost everything they say to each other is colored-poisoned, it might be said-by something bad that has happened in the past, whether it is the numerous examples of Tyrone's miserliness, or the corrosive effects of Mary's addiction, or Jamie's laziness and drunkenness. The family is like a cart stuck in a ditch.
The prison of the past is all the more tragic because the play shows not only the behaviors that led them into their current situation, but also what each of the Tyrones might have been had life taken a different course, had the prison walls not been built. As a young girl, for example, Mary had innocence, romantic ideals, and a strong religious faith centered on the Virgin Mary. That faith disappeared early in her marriage, and she desperately wants to rekindle it, because that would offer a way out of the prison. The Virgin can offer divine forgiveness, whereas for humans, forgiveness does not come so easily. In the end, Mary's only response to her situation is to sink deeper and deeper into the past, as if she is in a kind of sad dream.
Like Mary, Tyrone was quite different as a young man. He seemed to be on the threshold of a brilliant career, when he was inspired by Shakespeare's plays and praised by the great actor Edmund Booth for his performance as Othello. But he allowed his miserliness, his materialism and his drinking to dominate his personality, and before he realized what was happening, life began to turn sour for him. Tyrone's attitude to the prison of the past is to escape it through drink, which is the same attitude Jamie has. Even Jamie, the most cynical character in the play, had talent and enthusiasm once. It was he who first encouraged Edmund to take an interest in poetry, and he can still recite long passages of poetry himself. But for him, the prison walls descended when he first realized that his mother was a drug addict. He has no hope of escaping what the past has done to him.
Of the four characters, only Edmund has a chance of escaping from the prison. The key moment comes in Act 4, when he recalls the mystical experiences he had when he was at sea. These experiences gave him insight into the ultimate reality of life, a peace, joy and unity utterly beyond the normal range of human understanding. Although he has not been able to recapture those moments, he is resolved to try, in his creative work, to express them. As he says to his father, he will never a real poet:
I couldn't touch what I tried to tell you just now. I just stammered. That's the best I'll ever do. . . . Well, it will be faithful realism, at least. Stammering is the native eloquence of us fog people.
Edmund is aware of his limitations, but he is committed to making the effort to faithfully record the reality of things as he experiences them, even though he knows he will never feel at home in life and "must always be a little in love with death." It is, in his own way, a heroic stance. Edmund is committed to the future, to escaping the prison of the past.