Marley tries to help Scrooge
1. Marley regrets that he didn't change his ways whilst he was alive - it's too late for him to avoid suffering. All he can do is offer Scrooge the chance to escape the same fate. Theme - Redemption - Scrooge is lucky - Marley implies that most people are already doomed to their fates, but Scrooge will get one last chance at redemption
2. He has stood invisibly at Scrooge's shoulder for "many a day" in the past. He acts as a kind of hellish guardian angel to Scrooge
3. Marley says that his presence now is "a chance and hope" of his own "procuring". This suggests that he's tried (and succeeded) to find a way to help Scrooge and give him a chance to save himself
4. Marley is acting selflessly - he's helping a friend, even though he has no hope of redemption himself