Tiny Tim’s purpose is to pull on the reader’s heartstrings, and Scrooge’s! He represents all of the children living in poverty in the “surplus population” that Scrooge refuses to help. Dickens desperately wanted to help the poor, and children most of all. He made Tiny Tim as pathetic and sympathetic as he possibly could.
There is also a dramatic purpose of creating Tiny Tim. By making us feel sorry for the cute and cuddly Tiny Tim, and then announcing that he will die if Scrooge does not intervene, there becomes a real pressing need for Scrooge to reform. He is no longer just saving himself, he is also saving the boy’s life.
When Tiny Tim is first introduced, his Christ-like personality is revealed.
[He] hoped the people saw him in the church, because he was a cripple, and it might be pleasant to them to remember upon Christmas Day who made lame beggars walk and blind men see. (Stave 3, p. 32)
There is nothing at all objectionable about the boy. He is clearly the apple of his father’s eye and the baby of the family. Dickens further memorializes him in the last line, further demonstrating Tim’s importance to the book.
And so, as Tiny Tim observed, God Bless Us, Every One! (Stave 5, p. 56)
Tim is not just a symbol to us; he is a symbol to Scrooge as well. Scrooge is unaware that Bob Cratchit has a crippled son. He asks the spirit if Tiny Tim will live, and becomes upset when he hears the boy will die. The spirit angrily throws his earlier words back at him.
[If] man you be in heart, not adamant, forbear that wicked cant until you have discovered What the surplus is, and Where it is. Will you decide what men shall live, what men shall die? (Stave 3, p. 34)
By emphasizing “What” and “Where” here, Dickens reinforces that idea that Tim represents all of the poor and needy. Scrooge does regret saying this, and one of the first things he does when he recovers is send Bob Cratchit a turkey—probably thinking about how Tim will be eating it.
In the end, Scrooge becomes a “second father” to the boy, loving him like the son he never had and basically becoming a beloved member of the Cratchit family. Thus Tim symbolizes Scooge’s transformation, reformation and reclamation as well.