Puddleglum's Name as a Symbol
Puddleglum's name symbolises his rather pessimistic nature and tendency to look at the worst case scenario of every situation. "Puddle" conjurs up the image of gloomy puddles that are the result of long, monotonous, grey rainy days, the opposite of sunny and cheerful. "Glum" means to be gloomy or down in the dumps. The name symbolises his outlook on life perfectly.
The Serpent As A Symbol
The serpent symbolises evil throughout the book. Rilian's mother is killed by a serpent. The evil Queen who kidnaps him and is doubtlessly the same person also becomes a serpent when she is angered and at her most threatening. Each time a serpent appears evil is present and evil acts tend to happen.
Narnia and the Underground World as Allegories
Narnia is an allegorical representation of Heaven, created by a divine creator, in this case, Aslan the Lion. It is a place of good, of harmony and of fairness. The underground world occupied by the evil Queen is an allegorical representation of Hell, as it is filled with fires that change the way the people there perceive what is around them and also limits their ability to stay true to themselves. It is a place of violence and evil intention where inhabitants are trapped against their will.
Stone Tablets Allegory
Aslan charges Eustace and Jill with the task of looking for the words that are written on large pieces of stone. This is an allegory of God tasking Moses with looking for words on the stone tablets that became the Ten Commandments. Aslan's words that will free the people of Narnia are written on the tablets just as God's words that were to free the people of Egypt were written on the stone tablets for Moses.
Faith in Aslan as a Motive
Throughout the book, faith in Aslan is a constant motive. Initially, Jill is frightened of Aslan because he is a rather large lion, but even though she has never met him before is confident in having faith in what he tells her. Even when it seems that having faith in Aslan's instructions might cause them harm, for example, by untying the Prince when he is seemingly raving like a madman, they nonetheless have faith and untie him as Aslan has told them to do. This results in his returning to his Prince identity again and enables them to take him back to Narnia and ultimately keeping the Narnians safe and free from the evil of the Queen.
