Irony of Free Will
The contrast between Heaven and Hell is stark; the Ghosts from Hell are overwhelmed with the vivacity of the landscape and the intense real-ness of its existence. These wretched Ghosts are perfectly free to leave their land of inanity to live in this realm of the divine, but ironically they inevitably forego this opportunity and freely choose to return to their Godless existences in the grey city. This free will, bestowed by God as a gift, ironically leads to the eternal end of these egocentric spirits.
Irony of the Academic
One of the Ghosts of Hell visits Heaven and speaks to a Spirit (an inhabitant of Heaven), who tries to convince him that he is, in fact, in Heaven. Ironically, the academic is unable to believe this simple fact; he insists in vague terms that Heaven is less of a place than a state of being, and that all people can experience a sense of the heavenly in some form or another. Completely blinded to the fierce reality of Heaven, the academic cannot realize its existence even when experiencing it firsthand.
Irony of Sarah Smith
While in Heaven, the narrator watches a procession of heavenly beings heralding the presence of someone radiant and utterly brilliant. The narrator expects this person to be someone famous, but the reality is ironically different: it is a woman named Sarah Smith, unknown and unpraised on Earth, but who is characterized by such perfect humility that she stands out even among the spirits of Heaven.
Irony of the Spiritual Realms
As the narrator journeys to Heaven from Hell, he perceives it as a vertical ascent into the heavens from the ground. He comes to realize, however, that the reality is utterly different from his perception: Hell is not under Heaven, but merely so ontologically insignificant in comparison that the entirety of Hell could fit inside a single atom of Heaven.
Irony of the Sun
At the novel's end, the narrator looks to the horizon to behold the rising sun. When faced with this light, George MacDonald (the narrator's spiritual guide) appears to calmly and contentedly relish its appearance. Its impact on the narrator, however, is ironically different: it causes him to scream in pain from the sheer brilliance of its light, something his mortal mind cannot comprehend, jolting him out of his dream back into the 'real world.'
