To the Autumnal Moon

Samuel Taylor Coleridge's "To the Autumnal Moon" is a terrific allegorical sonnet in which Coleridge compares the Autumnal moon to Hope. He uses several structural techniques to support this metaphor. Coleridge uses paradoxical word parings, connections between first letters of words, and the Volta to convince the reader that the autumnal moon represents hope.
Several times throughout the poem Coleridge pairs two words with seemingly little connection or even opposite ideas, such as "Hope" and "the Autunmal Moon." The very first words of the poem are an example of this, as mild would hardly be used to describe a splendor of any sort. Similarly, a veil has quite opposite properties than "fleecy," yet that is how he describes it. Further, blackness is not something that one would typically think could be gathered, and its connotation is more of emptiness than togetherness. Another example of this antithesis is manifest in "placid lightning," which is an oxy moron, for lightening is anything but placid. All of these contrasting word pairings set up the ultimate paradoxical paring between the moon itself and the idea of hope.
He also uses alliteration and capitalization of the first letters of certain words to support his comparison between the autumnal moon and hope. In the first lines of the poem, he uses alliteration in multiples of twos which seem to be setting up a comparison between two things. The phrases "various-vested" and "wildly-working" create pairs in the reader's head right off the bat, helping to set up the ultimate pairing of the moon and hope. Further, the use of capitalization in certain words in the sestet makes it clear that he is talking about both the moon and hope throughout the poem. One might think that the comparison to hope is just one line thrown in there to help describe the autumnal moon, yet "Hope" is capitalized, as are "Despair" and "Care" later in the sestet. This link shows that it is hope that he is talking about, not just the autumnal moon as it appears on the surface.
Finally, it is the Volta itself that actually reveals the comparison he is trying to make throughout the poem. It is important to note, first, that although he is an English poet, this poem is written in Petrarchan style, which allows for several lines after the volta, rather than just two. These six lines begin with the volta itself, or the realization that the autumnal moon, what he has been describing throughout the poem so far, is like hope. Then he seems to run with this idea in the rest of the sestet, which is ambiguous in that these lines could easily be describing the autumnal moon, when in fact, they are describing Hope. When the reader looks back, he may then realize that the whole poem is in fact describing hope more than the autumnal moon.
This sonnet by Samuel Taylor Coleridge appears to be a simple ode to the autumnal moon. However upon closer inspection, it is really a comparison between the autumnal moon, with its beauty and promise, and hope, which is equally as beautiful and promising. Coleridge uses paradoxical pairings, alliteration and capitalization of first letters, and the volta to drive home his comparison to the reader.