I would take a certain issue with the observation that Bunyan invokes his own imprisonment when he writes about the man in the iron cage. Certainly Bunyan would have been sensitive to the idea of imprisonment, and this sensitivity could very well have emboldened his passion to warn others of the unwanted consequences of certain behaviors, but I believe there the similarity ends. Bunyan had been imprisoned for preaching the gospel without an official sanction from the religious establishment of the day; the unjust result of extreme obedience to God. The man in the iron cage had created his own prison with bars of freedom, so to speak. He had so indulged his freedom to do as he pleased in this life that he had gone well past the point of no return, and it had become impossible for him to turn back. So, in very much an opposite fashion from Bunyan, this man's imprisonmnent was a justified result of extreme disobedience to God. This illustration was meant as a warning to others of the dangers of indulging too deeply in the pleasures of this life. The man spoke of several things to Bunyan relating to his punishment, mentioning the grieving of the Spirit as well as the hardening of his heart, a fairly common theme in scripture. These things are antithetical to Pilgrim's "progress".