In A Christmas Carol each character is symbolic because the story is allegorical in a sense.
Scrooge, the old miser who cares about no one, symbolizes the redemptive quality of human nature. Anyone can change, no matter how terrible and hopeless the person seems to be.
“Men's courses will foreshadow certain ends, to which, if persevered in, they must lead,” said Scrooge. “But if the courses be departed from, the ends will change. Say it is thus with what you show me!” (ch 4, p. 50)
Scrooge can change, so we all can too. Marley’s Ghost is another symbol of change, because he arranges for Scrooge to have a rare opportunity—to see himself for what he really is.
The Ghost of Christmas Past symbolizes the power of our past, and how it affects us. We are all instruments of our past. It affects us, even if we would like to forget it. The Ghost reminds Scrooge that his old master, Fezzywig, made him happy, but not with money.
“Why! Is it not? He has spent but a few pounds of your mortal money: three or four perhaps. Is that so much that he deserves this praise?” (ch 2, p. 24)
The ghost reminds Scrooge that there was a time in his life when he had hope for himself, and when he could be carefree. All of us are affected by our past. Scrooge’s fiancé left him because he began to care more about money than her, and that hurt him. The ghost reminds him. All of us have events in our life that were foundational, even if we don’t recognize it.
The Ghost of Christmas Present encourages Scrooge to look at the poor and helpless. He reminds Scrooge that he has an obligation to his employees and his family, and to his fellow man.
This boy is Ignorance. This girl is Want. Beware them both, and all of their degree; but most of all beware this boy, for on his brow I see that written which is Doom, unless the writing be erased. (ch 3, p. 40)
The Ghost reminds all of us that we are responsible for everyone around us, because their present is our present—and their future is our future.
Tiny Tim also represents the poor and helpless, and reminds us that they are cute and innocent.
The Ghost of Christmas Yet to Come symbolically reminds us that what we do now shapes our future. The ghost shows Scrooge what will become of him if he doesn’t change.