Shelley's cave

Shelley’s mobilized reflections on poetry, like the poetry in which they are brilliantly thematized, engage a terrifying "Abyss" whose "secrets" remain to his skeptical frame of mind forever sealed. Poetry thus becomes for him a form of magic, which he images in Alastor as the dream

Of dark magician in his visioned cave,

Raking the cinders of a crucible

For life and power, even when his feeble hand

Shakes in its last decay.

(Shelley’s Poetry 86)

This same thematizing metaphor is present in Adonais, where Shelley describes his "weak hand" holding the thyrsus, which vibrates under the influence of his "ever-beating heart" (400). It is also present in his identification of poetry in his Defence with a "secret alchemy" that "turns to potable gold the poisonous waters which flow from death through life" (505). The "more select classes of poetical readers" (135), whom Shelley would initiate into the art of alchemy, have, in his speculative account, no illusions about the nature of metaphor. They know themselves, as Shelley himself warns in his preface to Alastor, to be momentarily "deluded" by "a generous error," "duped" by an "illustrious superstition" (69). In the absence of anything more certain, they also know that human civilization is precariously founded upon illusion, or maya (a notion encountered by Shelley in his study of the Hindu zodiac, described in his notes to Queen Mab ). That illusion is the vitality of metaphor endlessly inventing new relationships, the stability of which forever threatens its vitality.

from Ross G. Woodman, "Shelley, Percy Blysshe" in The Johns Hopkins Guide to Literary Theory and Criticism, 2005 (to see link, click title)