Shelley repeatedly described himself as an atheist, and yet in his poetry he frequently explored the possibility of god-like transcendent powers, divine inspiration, and prophecy. In many of his greatest poetic works (such as Mont Blanc, Ode to the West Wind, and Prometheus Unbound), Shelley frequently invokes biblical imagery to articulate essentially Christian values (hope, charity, love) while developing his own master themes of enlightened defiance, political liberty and the struggle toward self-control. In Prometheus Unbound, Shelley's Greek Titan is metaphorically “crucified” for his sacrifice to help humanity. His liberation follows a personal transformation that recalls aspects of St. Paul’s writing on self-mastery. It is unclear if Prometheus’ liberation is causally linked to his own imaginative renewal, or whether there are other forces (God, Necessity, inscrutable Powers) that are instrumental. The repeated inclination to invoke both classical and biblical writing while developing themes of personal autonomy and enlightenment is one of the most interesting aspects of Shelley's work, and one of the most representative qualities of Romantic writing more generally.