Shelley's essay focuses on the ideologies associated with the creation of poetry. For him, very specific aspects must be present for a poet to create a poem worthy of praise or criticism.

Poetry, in a general sense, may be defined to be "the expression of the imagination."

For the Romantic, the imagination was the most important tool of the poet. It was the imagination which made sense of the world around the poet. The Romantic poet did not use reason in composing poetry, as it was not something which broke upon the poet organically. Instead, the imagination, which is organic, was solely responsible for all the things which inspired the poet and her work.

A poet participates in the eternal, the infinite, and the one.

Here, Shelley refers to the idea that the poet's immortality relies on her success at weaving language, sound, and imagination into one timeless idea. This idea, in turn, becomes a poem. This poem, in turn, becomes a part of the eternal world, a world that the poet herself will not be a part of. The poet's participation in the infinite is only successful if she is able to create the "one." The "one," here, speaks to the art of the poet and the poem.

Poetry is ever accompanied with pleasure.

When one is able to appreciate poetry, Shelley says, one may will always find pleasure in reading it. Yet Shelley may not only be speaking about the reader: he may also be speaking about the poet, who, when she is able to bring everything inside her together to create something new through her art, tends to find pleasure in her success.