Long Day's Journey into Night is undoubtedly a tragedy--it leaves the audience with a sense of catharsis, or emotional rebirth through the viewing of powerful events, and it depicts the fall of something that was once great. The play focuses on the Tyrone family, whose once-close family has deteriorated over the years, for a number of reasons: Mary's drug addiction, Tyrone Jamie, and Edmund's alcoholism, Tyrone's stinginess, the boys' lax attitude toward work and money, and a variety of other factors. As the play is set, the parents are aging, and while they always hoped that their sons would achieve great things, that hope is beginning to be replaced by a resigned despair.
The play is largely autobiographical; it resembles O'Neill's life in many aspects. O'Neill himself appears in the play in the character of Edmund, the younger son who, like O'Neill, suffers from consumption. Indeed, some of the parallels between this play and O'Neill's life are striking. Like Tyrone, O'Neill's father was an Irish Catholic, an alcoholic, and a Broadway actor. Like Mary, O'Neill's mother was a morphine addict, and she became so around the time O'Neill was born. Like Jamie, O'Neill's older brother did not take life seriously, choosing to live a life of whores, alcohol, and the fast-paced reckless life of Broadway. Finally, O'Neill had an older brother named Edmund who died in infancy; in this play, Edmund has an older brother named Eugene who died in infancy.
The play, published posthumously, represents O'Neill's last words to the literary world. It is important to note that his play is not condemning in nature; no one character is meant to be viewed as particularly worse than any other. This is one of the play's great strengths; it is fair and unbiased, and it shows that many character flaws can be seen as positives when viewed in a different light. Thus, Long Day's Journey into Night invests heavily in the politics of language. It is a world in which there is a large weight placed on the weakness of "stinginess" versus the virtue of "prudence."
The play also creates a world in which communication has broken down. One of the great conflicts in the play is the characters' uncanny inability to communicate despite their constant fighting. For instance, the men often fight amongst themselves over Mary's addiction, but no one is willing to confront her directly. Instead, they allow her to lie to herself about her own addiction and about Edmund's illness. Edmund and Jamie do not communicate well until the last act, when Jamie finally confesses his own jealousy of his brother and desire to see him fail. Tyrone, likewise, can only criticize his sons, but his stubborn nature will not allow him to accept criticism. All the characters have bones to pick, but they have trouble doing so in a constructive fashion.
Most of the bones that need picking emerge in the past, which is remarkably alive for the Tyrones. Mary in particular cannot forget the past and all the dreams she once had of being a nun or a pianist. Tyrone too has always had high hopes for Jamie, who has been a continual disappointment. All the conflicts and the problems from the past cannot be forgotten, and, in fact, they seem doomed to be relived day after day. It is important to note that Long Day's Journey into Night is not only a journey forward in time, but also a journey back into the past lives of all the characters, who continually dip back into their old lifestyles. We are left as an audience realizing that the family is not making progress towards betterment, but rather continually sliding into despair, as they remain bound to a past that they can neither forget nor forgive.
The play is all the more tragic because it leaves little hope for the future; indeed, the future for the Tyrones can only be seen as one long cycle of a repeated past bound in by alcohol and morphine. This play was awarded the Pulitzer Prize when it was first published, and it has remained one of the most admired plays of the 20th century. Perhaps most importantly, it has achieved commercial success because nearly every family can see itself reflected in at least some parts of the play. The Tyrone family is not a unique family, and it is easy to identify with many of the conflicts and characters. The play has a unique appeal to both the individual audience member and to scholars of American drama, which explains its popularity and enduring acclaim.