"Alastor", like "Epipsychidion," reveals the mistake which Shelley made in thinking that the idea of beauty could become incarnate for him in any earthly form: while the "Hymn to Intellectual Beauty" recognizes the truth that such realization of the ideal is impossible.

The very last letter written by Shelley sets the misconception in its proper light: "I think one is always in love with something or other; the error, and I confess it is not easy for spirits cased in flesh and blood to avoid it, consists in seeking in a mortal image the likeness of what is, perhaps, eternal." But this Shelley discovered only with "the years that bring the philosophic mind," and when he was upon the very verge of his untimely death.
The following quotation is a fair specimen of the blank verse of "Alastor".

It expresses that longing for perfect sympathy in an ideal love, which the sense of divine beauty had stirred in the poet's heart:-- At length upon the lone Chorasmian shore He paused, a wide and melancholy waste Of putrid marshes.

A strong impulse urged His steps to the sea-shore.

A swan was there, Beside a sluggish stream among the reeds.
It rose as he approached, and, with strong wings Scaling the upward sky, bent its bright course High over the immeasurable main.
His eyes pursued its flight:--"Thou hast a home, Beautiful bird! thou voyagest to thine home, Where thy sweet mate will twine her downy neck With thine, and welcome thy return with eyes Bright in the lustre of their own fond joy.
And what am I that I should linger here, With voice far sweeter than thy dying notes, Spirit more vast than thine, frame more attuned To beauty, wasting these surpassing powers In the deaf air, to the blind earth, and heaven That echoes not my thoughts ?" A gloomy smile Of desperate hope wrinkled his quivering lips.
For Sleep, he knew, kept most relentlessly Its precious charge, and silent Death exposed, Faithless perhaps as Sleep, a shadowy lure, With doubtful smile mocking its own strange charms.
William, the eldest son of Shelley and Mary Godwin, was born on the 24th of January, 1816.