The tone throughout Prometheus Unbound alternates between critical and incisive and hopeful. Shelley's political motivations in the text are clear; undoubtedly, it was intended to allegorize the state of England's government at the time of Shelley's writing. Though appealing to a revolutionary spirit, Shelley does not come across as didactic or vengeful. Instead, the tone of the work remains forgiving throughout, centering love instead of revenge.
This particular aspect of tone—indeed, the at times seemingly foolhardy excess of hope in the story—stems from Shelley's connection to Christianity. In general, the Christian faith centers the concept of forgiveness as an ideal, with missives such as "turn the other cheek" and "love thy neighbor as thyself" littering the Old and New Testaments of the Bible. Jesus, whom Prometheus may have been intended to represent, had much to say on the subject of forgiveness, believing as he did in radical empathy for one's enemies. In Matthew 18:21-22, Jesus even replies to one of his disciples that they should forgive someone not just seven times, but seventy-seven times. While the hopeful tonal elements in Prometheus Unbound may at first appear as naïveté, this viewpoint on forgiveness—while rarely perfectly practiced—would have been a common subject for preachers during the time period in which Shelley lived.