The central theme of Miller’s play is that of social responsibility. This is the duty of an individual to the society in which he lives.
Keller is able to pin the crime on Deever and maintain his own status in society, even though his actions are immoral.
The sale of the cylinder heads is similar to a stone dropped into water, with endless rippling repercussions.
Keller’s actions were not motivated by a desire to harm. His concern was purely to give his family the best possible life. In this regard, we could all have committed this crime.
The tree in the garden symbolises the family’s attempt to keep the memory of Larry alive. However, it also symbolises the family’s belief that Larry is literally still alive. When it is struck by lightning, we see the suggestion that he is dead, but it also coincides with Ann’s visit, and she destroys the fantasy that Larry is still alive (accomplished with Larry’s suicide note). Kate interprets the destruction of the tree as a sign that Larry will return.