Joe defends his crime of knowingly sending out 120 faulty plane engine parts by saying he did it to safeguard the economic welfare of his family and to protect a business it had taken years for him to build, but which could be ruined in a short time period should his buyers loss faith in his products. He also says he believed that the army would have discovered the flaw in the parts and refused to install them. In other words, he kicked the can down the road.

An important theme of the play is that if Americans don't change their ways and start putting people ahead of profits and the good of the whole nation ahead of personal self-interest, all the young men who died to protect America did so pointlessly. Joe's rationalizations illustrate exactly the mindset that the play hopes to condemn. Joe cost people, including his own son, their lives because he cared more about money that human lives.

Joe finally understands what he has done, saying the young men who died due to his faulty engine heads were "all my sons." He realizes that the lives of people outside of his family matter. This new awareness leads him to commit suicide, but it encourages the audience to look at bigger picture than their own self interest.