Priestley presents responsibility as a key theme in An Inspector Calls. The older characters, Mr and Mrs Birling, refuse to accept responsibility for Eva Smith's death, while the younger generation, Sheila and Eric, do accept it. This shows that Priestley wanted the audience to see that everyone in society has a duty to look after others.
Mr Birling refuses to accept any responsibility for Eva's fate. He insists 'a man has to mind his own business and look after himself and his own', which shows that he believes only in self-interest and rejects collective duty. Priestley uses Birling to represent selfish capitalists who only care about profit. The audience would dislike Birling because he does not care about Eva at all.
Sheila, however, accepts responsibility. When she learns what she did, she says she will 'never, never do it again'. The repetition of 'never' shows that she genuinely regrets her actions and wants to change. Priestley uses Sheila to show that the younger generation can learn from their mistakes.
At the end of the play the Inspector says 'we are members of one body'. This is Priestley's message to the audience that everyone is connected and should take responsibility for each other. Priestley was a socialist and believed in a welfare state where people helped one another. He set the play in 1912 but it was first performed in 1945, so the audience could see how attitudes had changed.