Explain the theme of morality versus blame.

Both of these address your question,

The Past

All My Sons is a play about the past. It is inescapable--but how exactly does it affect the present and shape the future? Can crimes ever be ignored or forgotten? Most of the dialogue involves various characters discovering various secrets about the recent history of the Keller family. Miller shows how these past secrets have affected those who have kept them. The revelation of the secrets is presented as unavoidable--they were going to come out at some point, no matter what, and it is through Miller's manipulation of the catalysts that the truths are all revealed on the same day. Whilte the revelations are unavoidable, so are their fatal consequences.

Denial and Self-Deception

How do we deceive ourselves and others? We select things to focus on in life, but do we also need to deny certain things in order to live well? What toll does denial take on the psyche, the family, and society? Two main facts about the Keller family history must be confronted. One is Larry's death, and the other is Keller's responsibility for the shipment of defective parts. Mother denies the first while accepting the second, and Keller accepts the first while denying the second. The result is that both characters live in a state of self-deception, willfully ignoring one of the truths so that the family can continue to function in acceptable ways.