Within the story, I feel that it's important that we understand that Priestly uses the Inspector to be his own voice. Maybe more importantly, he wants to portray the voice of society's moral conscience.
There is a definate contrast between characters, Mr & Mrs Birling being so defiant in their ways, never accepting their wrong doings. Then there's Inspector Goole, a mysterious figure who appears from no where... (well the front door actually)
I feel that the Birlings have been used as a figure, showing society what we are, yet what we shouldn't be. Each of the characters seem to act very dramatically towards the situation, denying all responisbility feeling that it's not an issue of theirs. Where as in reality, we understand that Priesty is trying to convey the idea…