stripped by away by his essentially immoral character, just as Willy Loman had lived a lie in his presumed fealty to his marriage to Linda while concealing the secret of his affair -- a secret to which Biff was sadly privy.

All My Sons is consistent in its portrait of a deeply-flawed man, a businessman who prospered during World War II as a manufacturer of engine parts for fighters. Joe Keller, though, carries within himself the most tragic of secrets, that he was responsible for the deaths of American pilots, possibly including his missing son, Larry, and, moreover, that his duplicity and cowardice sent his business partner to prison. That Larry is presumed, based upon his letter, to have deliberately crashed his plane rather than live with the knowledge of his father's perfidy is a powerful unseen example of the play's tragic theme. As Miller's play progresses towards its tragic conclusion, the connection between Joe's actions and the consequences of those actions become more and more clear, and difficult to deny. As his wife, Kate, remarks to second son Chris in the second act of All My Sons: 

“Your brother’s alive, darling, because if he’s dead, your father killed him. Do you understand me now? As long as you live, that boy is alive. God does not let a son be killed by his father. Now you see, don’t you? Now you see.”

And so, with this mentality dominating the family's collective psyche, they inch through life struggling to deny reality. The meaning of the title, All My Sons, lies in Joe's own form of denial, in which, in Act III, he states, with respect to his responsibility to his family, “I’m his father and he’s my son, and if there’s something bigger than that I’ll put a bullet in my head.” Joe will, of course, put a bullet in his own head rather than live with his family, and his former business partner's family, fully cognizant of his crimes, both legal and moral. Joe's attempts at reconciling his actions with the loss of one son to death and the other to shattered dreams (Chris: “I know you’re no worse than most men but I thought you were better."), flounder under the weight of his guilt. Joe has been a committed father to his sons, but he knows he has failed in the broader picture. In one of the play's more famous lines, and the one to which the play's title refers, Joe acknowledges that his responsibilities extended beyond his own home and to those who flew aircraft powered by engines that incorporated his parts: “Sure, he was my son. But I think to him they were all my sons. And I guess they were, I guess they were.”

The impact of the ending of Miller's play is a powerful and poignant reminder of collective responsibility and of the emotional toll exacted by the decision to live a life of duplicity and denial. Miller's protagonists are not evil; they are representative of humanity, and, consequently, are imbued with imperfections of character. Joe's decision to kill himself is the only act left to him that may leave him with a measure of pathos, if not of dignity.

At the end of the play, Chris finally gets through to his father when he reads him Larry's letter to Ann. In the letter, Larry states,

Yesterday they flew in a load of papers from the States and I read about Dad and your father being convicted. I can't express myself. I can't tell you how I feel ... I can't bear to live any more.

At this point, Joe accepts that his actions in selling the cracked cylinder heads to the army led to the death of twenty-one pilots and to the suicide of his beloved son. He fully realizes for the first time that he was responsible for the death not only of his son but of other flesh-and-blood human beings just like his son. The dead pilots are no longer simply names on a casualty list, but real people to him.

Joe goes in the house. Both Mrs. Keller and Chris believe he is putting his jacket on so he can go and turn himself in for his crime. Mrs. Keller attacks Chris by saying that the war is over and that there is no value now in Joe sitting in prison. She says desperately that they are sorry over what happened, but what else is to be done at this late date? Chris responds by saying,

Once and for all you can know there's a universe of people outside and you're responsible to it.

At this point, they hear a gunshot from inside the house. Joe has committed suicide over guilt at what he has done. Mrs. Keller begins crying out her husband's name, while Chris turns to her and says he never meant for his father to kill himself.

The play ends tragically with Joe's death, but at the same time. it reminds us that we live in a bigger world than ourselves and our immediate families.

It is possible to see positive elements at the end of Arthur Miller's All My Sons.  At the end of the play, Chris tells Ann that their relationship is over and that he is going to seek a new life elsewhere.  Although it is tragic that their relationship comes to an end, it is positive that Chris realizes that he needs to rethink his position in life in light of all the secrets that have been unearthed about his family.  Chris questions the role that he had in the war in light of his father's and brother's actions, and he recognizes that he needs time to deal with these conflicting feelings.  So, this is a positive element.

Further, Kate now knows that Larry will never come home from the war based on the letter that he sent to Ann before he took his last flight.  Kate can now deal with Larry's death rather than dwell on the false possibility that he might come home.  In the long run, this will be a positive move for Kate.

So although Joe commits suicide and many relationships in the play seem to come to tragic ends, there are positive elements that arise as a result.