"INSPECTOR" who played a part in someone's "demise"
Responsibility

Embodiment of social responsibility
The "Inspector" says "It's better to ask for the earth than to take it"
The "Inspector" says "Public have responsibilities as well as privileges"
Inspector

Plays a part in Eva's demise
Priestley was appalled at the period between WWI and WWII since it brought widespread poverty
The inspector is an embodiment of social responsibility
Public men have responsibilities as well as privileges
The inspector is not defending him, but Sheila must understand that a lot of young men are hard-eyed and down-faced
J.B. Priestley was born in Bradford and saw poverty in his neighbourhood frequently, which influenced his socialist values
Eternal recurrence 

Ouspeskeys theory - change has to take place by leaning for your actions
The play ends with the family being left alone in darkness symbolising that they are now isolated from society and have been punished for their sins.
Perhaps, it can be inferred that Priestley was trying to prevent eternal recurrence as he was greatly influenced by the Russian Philospher Ouspensky who believed that if man didn’t learn from their
behaviour and learn from their mistakes they would live in a never ending cycle of the same behaviour
we are all members of one body
we are all responsible for eachother
socialist ideas were very popular at this time because people had just come out of WW1 where there was great inequality between classes
Priestly wanted to show how the upper class treated the lower class badly and how they could get away with it due to their wealth and status
the idea of socialism is that everyone is equal and no-one is better than anyone else