jingle The way I look at it is the play is not meant to be taken literally. I think it is a dramatic device to examine issues of wealth, class and power - it's nothing to do with a crime being committed. It doesn't really matter who you think the Inspector is meant to represent - God or a ghost or a collective conscience - his purpose is to confront the truths that are usually hidden. The girl and the various ways in which she is mistreated - is a representation -meant to represent the experience of the working classes who were exploited in the workplace and in society generally.
I think the reason why there were two Inspectors was because the first one gave an opportunity for people to examine their consciences and alter their behaviour. After the revelations of the first Inspector, the factory owner and his wife and the daughter's fiancée seemed to be upset that their actions had contributed to the girl's suicide. But as soon as they found out the Inspector was "bogus", what had appeared to be remorse was shown to have been feigned because their supposed regret was quickly replaced by relief and laughter - and then indignation.
Probably different people have different interpretations of why there is a "bogus" Inspector and then a real one. I suppose religious people might think that the first Inspector represents God who provides an opportunity for wrong doers to repent, whereas the second Inspector represents punishment at the "day of reckoning". (It also provides a satisfyingly dramatic and sinister end to the play).
I think it is a brilliant play, but each to his or her own I suppose.