An allegory, as you know, is different from symbolism (which can stand for many things). An allegory has a one-to-one kind of symbolism (Christian = Bunyan). So, Pilgrim's Progress details a grueling physical journey that is directly analogous to the the spiritual journey of how a Calvinist must get to heaven. To Bunyan, the goal (heaven / Celestial City) is the only thing, and everything along the way is expendable: family, home, material possessions--all of which are only temptation, as they ground the pilgrim in the earthly and not the spiritual.
Some critics say that there are many ways for the pilgrims in the novel to reach heaven, but according to Bunyan, in his Calvinist sermons, there is only one way. He even made a map detailing the direct path and pitfalls along the way. So, to understand the Pilgrim's Progress, we must understand Bunyan, or Christian incarnate, and Calvinism.
The young Bunyan suffered from recurring nightmares where he was tormented by demons, dragons, monsters, wicked spirits, and the prospect of eternal damnation. These dreams obviously helped shape his vivid imaginative writing style and became a source of inspiration for framing Pilgrim's Progress.
At the age of twenty, Bunyan, converted to militant Calvinism much like Saul became Paul on the road to Damascus. After this, his goal was on salvation: to "escape from a literal hell" and to "achieve a literal heaven."
So says Enotes:
For all the characters who successfully complete the journey, far more do not make it. Some are obviously opposed to the idea of pilgrimage and have set themselves on courses which keep them trapped in the affairs of this world. Characters with names like Obstinate, Atheist, Prejudice, and Ill-will are committed to the earthly world. But there is a third category of character: people whose errors are not as immediately obvious as those of the enemies of pilgrimage, but whose failings nonetheless condemn them to perdition. Perhaps the most poignant figure in The Pilgrim's Progress is Ignorance, who arrives at the gate to the Celestial City only to be bound hand and foot and put in a doorway that leads to hell. In his earlier scenes, Ignorance seems possessed of an engaging good will, as do Talkative, Pliable, and others. However, all these characters lack the requisite knowledge, understanding, or commitment to make a pilgrimage that requires complete devotion to the teachings of Christ.
So, Pilgrim's Progress is a militant Calvinist's handbook outlining the way to heaven and the escape from hell. Here are some more points of allegorical Calvinism :
A. Born into original sin
B. Goal of salvation
C. Regeneration precedes conversion
D. Pilgrim's Progress is Bunyan's dream-vision:
1. Torments (fear of hell): reason for his conversion
2. Allegorical nature: vague meanings, multiple interpretations, intuition
3. Divine inspiration: from God or from subconscoius?
E. Mythical Spiritual Journey
1. Begins at awareness of sin
a. Bunyan's greatest fear was that his faith was inadequate for salvation
b. Calvinist belief in total depravisty/original sin
2. Lost in the wilderness of this world (alienation)
3. Must "flee the wrath to come" (Old Testament)
a. From City of Destruction (Sodom/Gom.--from Bible)
b. Leave wife/child behind
4. Journey toward Salvation (at expense of family, home)
1. Focuses life around special purpose or goal; everything(one) is second-rate
2. Realizes infinitely important goal cannot be reached, inevitably, for whatever reason.
4. Evangelist (bringer of good news [Gospels], New Testament)
1. Comes to his aid; tells him to stay on path to Wicket Gate
2. Seems too simple