social class - as a morality play
1) Gerald and Mr Birling as capitalist symbols - "what happened to her then... may have driven her to suicide" - ties everyone to her death. Upper class/capitalists shouldn't be above the law, or free to oppress the lower classes, but they continue to do so. / Mrs Birling & Mr Birling is the epitome of class prejudice "girls of that class," "if you don't come down harshly on some of these people, they'd soon be asking for the Earth." - the hyperbole shows how upper classes are aware of the poor living standards for the poor, but still perpetuate the cycle of poverty.
3) Sheila and Eric - highlight selfishness of young people of that class; also show change -> they are remorseful. Sheila's obliviousness "pretty and pleased with life", she is antithesis of Eva, and yet still becomes a socialist mouthpiece and proxy of the Inspector forms hope for younger generations. Both change, thanks to the inspector, who is a representation of socialism -> shows that anyone is capable of change, and that the younger generations are the voices of the future.
4) the Inspector exposes the ignorance of the upper classes -> "pink and intimate" to "brighter and harder." / holds a mirror up to the character and us, had a message of revolt: "fire and blood and anguish." - WW2.