The Ghost of Christmas Present shows Scrooge numerous sceneswith several aims. In viewing the family in the coal miner's hut, the men working at the lighthouse, and the crew of the ship, he shows Scrooge that the celebrating Christmas is not something that has to be earned, as Scrooge intimated in Stave 1 in his conversation with his nephew when he asks what right he has to be merry since he's poor. The Spirit of Christmas is found in all walks of life. In showing him Tiny Tim at the Cratchitt's family dinner, he gives a face to the poor whom Scrooge so callously condemned in Stave 1 with his remarks to the charity collectors. Just as important, though, is the idea that the Ghost of Christmas Present shows Scrooge that it isn't too late to "mend fences" and have a positive turn in his life. To hear that his nephew bears no ill will toward him must have made the thought of reconciling with him far less intimidating than it would have been otherwise. To hear the spirit imply that if he was able to change things for Tiny Tim he would live to see the next Christmas must have given him great motivation. The Ghost of Christmas Future served to show him to hopelessness of continuing on his present course. To see how callously his possessions were stolen and sold at the pawn shop and how little regard he held among his fellow men when listening to peoples' reactions would be painful for anyone. The "reality" of the death of Tiny Tim struck a chord in him, and the looming fear of the grave gave him an urgency with which to apply the principles of his newly-found life.
In short, the Ghost of Christmas Past helped him realize his regrets, the Ghost of Christmas Present helped show him the hope of change, and the Ghost of Christmas Future helped show him the "fruits" of his current course and gave him the urgency needed for his transformation.