One theme of "The Eolian Harp" is gratitude. One needs no knowledge of Coleridge's philosophy to understand this lyrical poem as an outpouring of joy at life and the universe. The speaker is young, newly married, in love with his wife and with life, and finds the world a beautiful place. He pours his overwhelming sense of gratitude, optimism, and joy into his verse:

Rhythm in all thought, and joyance everywhere—

Methinks, it should have been impossible

Not to love all things in a world so filled

A second theme is love of nature. Like a good Romantic poet, Coleridge celebrates the natural world. This poem abounds with joyous nature imagery, and nature reflects the beauty and order of the cosmos. There is a sweet sadness and loveliness in the imagery of the departing day:

our Cot [cottage] o’ergrown

With white-flowered Jasmin, and the broad-leaved Myrtle

(Meet emblems thy of Innocence and Love!)

And watch the clouds, that late were rich with light,

Slow saddening round, and mark the star of eve

Serenely brilliant (such would Wisdom be)

Shine opposite!

Whilst through my half-closed eyelids I behold

The sunbeams dance, like diamonds, on the main

A third theme of the poem is to question the nature of the universe. The speaker has a flight of fancy in which he wonders if all of "animated nature" is conscious and alive with thought as humans are. What if the various parts of nature are "organic harps" that are "At once the Soul of each, and God of all?" Is nature consciously alive? Is nature God? The speaker, in the final stanza, comes back to a conventional understanding of a Christian God rather than "vain Philosophy" and remembers he is a sinful and forgiven man. Nevertheless, he records his flight of fancy, suggesting it could possibly be true, opening us as readers to ponder the nature of the universe.