From Bunyan’s Pilgrim’s Progress:
“Now a little before it was day, good Christian, as one half amazed, brake out in passionate speech: What a fool, quoth he, am I, thus to lie in a stinking dungeon, when I may as well walk at liberty. I have a Key in my bosom called Promise, that will, I am persuaded, open any lock in Doubting Castle. Then said Hopeful, That’s good news; good brother pluck it out of thy bosom and try.
Then Christian pulled it out of his bosom, and began to try at the dungeon door, whose bolt (as he turned the Key) gave back, and the door flew open with ease, and Christian and Hopeful both came out. Then he went to the outward door that leads into the Castle-yard, and with his Key opened that door also. After he went to the iron Gate, for that must be opened too, but that Lock went very hard, yet the Key did open it. Then they thrust open the gate to make their escape with speed; but that gate as it opened made such a creaking, that it waked Giant Despair, who hastily rising to pursue his prisoners, felt his limbs to fail, for his fits took him again, so that he could by no means go after them. Then they went on, and came to the King’s High-way again, and so were safe, because they were out of his jurisdiction.
Now, when they were over the stile, they began to contrive with themselves what they should do at that stile to prevent those that should come after from falling into the hands of Giant Despair. So they consented to erect there a pillar, and to engrave upon the side thereof this sentence — ‘Over this stile is the way to Doubting Castle, which is kept by Giant Despair, who despiseth the King of the Celestial Country, and seeks to destroy his holy pilgrims.'”
This is an extremely popular and often-referenced scene that reveals Bunyan’s anti-Biblical belief that believers can become unbelievers for a period of time. Speaking of the faith of Abraham, God through the apostle Paul says:
“And being about a hundred years old, not weakening in faith, he did not consider his body to have died already, nor yet the death of Sarah’s womb, and did not stagger by unbelief at the promise of God, but was empowered by faith, giving glory to God, and being fully persuaded that what He has promised, He is also able to do” (Romans 4:19-21).
Bunyan’s “Christian” and “Hopeful” reveal their darkened ignorance and unbelief concerning Jesus Christ and His atoning blood and imputed righteousness as the SOLE ground of acceptance with God (Romans 10:1-4). They doubted God’s promise to save His people conditioned on the atoning blood and imputed righteousness of Christ ALONE. The key called “Promise” was hidden away in “Christian’s” blackened bosom which revealed that “Christian” was bereft of and not submitted to the righteousness of God revealed in the gospel of Jesus Christ (Romans 10:3).
The primary reason “Hopeful” and “Christian” were supported from utter despondency at the hands of Giant Despair was because they did NOT yet despair of their own righteousness as the sole ground of acceptance before God. If “Christian” and “Hopeful” HAD despaired of their own self-righteousness and hoped in the atoning blood and imputed righteousness of Christ alone, they would never doubt, they would never be shaken, for they would have had their foundation on the Rock of Jesus Christ:
“Truly my soul waiteth upon God: from him [cometh] my salvation. He only [is] my rock and my salvation; [he is] my defence; I shall not be greatly moved. … My soul, wait thou only upon God; for my expectation [is] from him. He only [is] my rock and my salvation: [he is] my defence; I shall not be moved. In God [is] my salvation and my glory: the rock of my strength, [and] my refuge,[is] in God” (Psalm 62:1-2,5-7). “They that trust in the LORD [shall be] as mount Zion, [which] cannot be removed, [but] abideth for ever. As the mountains [are] round about Jerusalem, so the LORD [is] round about his people from henceforth even for ever” (Psalm 125:1-2).