Memento mori was an instruction that all Christians received to live good lives because the goodness of their choices in life dictates what will happen to their soul in heaven
The ghost of Christmas yet to come showing Scrooge his own grave
This is his memento mori, the thing that's going to change his behavior
Marley's ghost
Feels regret, looks back on his life and says he should have looked after the poor
Marley's regret is that in life we should have looked after the poor, otherwise our souls will be troubled in the afterlife
Marley's haunting of the earth is not a particularly Christian belief
Dickens uses Marley to show that if we do not act to help the poor ourselves, our own souls will be troubled if not in this life than in the afterlife
Dickens is talking to businessmen through Marley's ghost
Dickens' message expressed by Marley's ghost is that we all must use our powers to help those who need it, the poor
Scrooge sees the ghosts of businessmen in Stave 4
They look miserable, having lost the power to do good in life
Scrooge revisits his lonely, unloved childhood self
He realizes he is cruel to the poor carol singer because that's how his father treated him
Scrooge realizes he is repeating patterns of attachment from his childhood in his adult life
Scrooge's change is motivated by a desperation to change Tiny Tim's fate, giving Scrooge a second chance at fatherhood
Scrooge misses the love of Belle's eldest daughter, a daughter who could have called him father
Dickens suggests that children are what bring life meaning, that's why Scrooge becomes a second father at the end
Scrooge is motivated to change not out of worry for his own death, but the consequences of him dying and not being able to help others
Scrooge wants to make life better now for the poor, not just ensure his own soul goes to heaven
The warning about the children Want and Ignorance is a warning to society about the dangers of not educating the poor, especially boys, who may turn to violence and civil unrest
Dickens introduces this warning of memento mori halfway through the novel, while at the end he focuses on the redemption of treating the poor like your own children