Percy Bysshe Shelley, from Prometheus Unbound
Though he based Prometheus Unbound on what was known of a lost drama by Aeschylus, Shelley went beyond his classical model, in the belief, as his Preface explains, that Aeschylus’s account brought the struggle between Prometheus and Jupiter to a feeble conclusion. Aeschylus’s way of bringing about a reconciliation between Prometheus and Jupiter, Shelley asserted, failed to do justice to Prometheus's heroism. In this passage from the Preface, that heroism is contrasted with Satan’s.
The only imaginary being resembling in any degree Prometheus is Satan; and Prometheus is, in my judgement, a more poetical character than Satan because, in addition to courage and majesty and firm and patient opposition to omnipotent force, he is susceptible of being described as exempt from the taints of ambition, envy, revenge, and a desire for personal aggrandisement, which in the Hero of Paradise Lost interfere with the interest. The character of Satan engenders in the mind a pernicious casuistry which leads us to weigh his faults with his wrongs and to excuse the former because the latter exceed all measure. In the minds of those who consider that magnificent fiction with a religious feeling, it engenders something worse. But Prometheus is, as it were, the type of the highest perfection of moral and intellectual nature, impelled by the purest and the truest motives to the best and noblest ends.
— From Preface to Prometheus Unbound (1820)