There's a famous saying around poetry campfires that "form is content." That sounds smart, and maybe even interesting, but what does it mean and what does it have to do with "Yet Do I Marvel"? Pull out your snuggie and get comfy, because we're going to break it down for you. See, the way Cullen delivers his message through the poem is as important as what his message is. What he's saying and how he's saying it are so intertwined, they're almost indistinguishable.
Let's start with the basics. "Yet Do I Marvel" is a sonnet. There are basically two types of sonnets: the Italian and the English. We'll focus on the English sonnet, since that is the form Cullen uses. This sonnet is fourteen lines long (all sonnets are, traditionally), and employs a regular rhyme scheme. A rhyme scheme isn't a secret plot to overthrow the government—it's a strict pattern of end rhyme in a poem.
In this case, each pair of rhymed words is represented by a letter. Let's look at the first four lines (a.k.a. the first quatrain).
So, "kind" and "blind" rhyme, right? That rhyme would be represented by the letter A because it's the first rhyme. And since "why" and "die" rhyme, they would be represented by the letter B because they're the second rhyme that appears in the poem. Every time a new rhyming sound appears, a new letter is assigned to that rhyme. Here's a breakdown of the rhyme scheme with the rhyming words that appear at the end of each line:
So that's part of the form, but how is it content? Look at which words Countee Cullen rhymes in this poem. For example, he rhymes "kind" with "blind," right? Those two words contradict each other in the poem. The speaker says God is "kind" but then gives an example of suffering: the "blind" mole. So, just like there's a paradox between God's kindness and the unfortunate blindness of the mole, Countee Cullen rhymes two contradictory words to reinforce the speaker's confusion. Make sense? Now it's your turn to go through the rest of the rhymes and see what you can uncover. You'll be a sonnet pro in no time.
Like all traditional sonnets, this one is written in iambic pentameter. An iamb is a metrical foot that consists of one unstressed syllable followed by one stressed syllable—daDUM. Pentameter just means that there are five of these feet, all in a row. Look at the first line of the poem. We'll put the stressed syllables in italics and slashes between each foot:
I doubt/not God/is good,/well-mean/ing, kind
Hear it? It goes daDUM daDUM daDUM daDUM daDUM. That's a perfect line of iambic pentameter, right there in the flesh. And for much of the poem, the meter stays just that perfect. Countee Cullen measured out his poem perfectly. He wanted an exact sonnet, but why?
One reason may be because he was writing during the Harlem Renaissance. He was a popular poet back in the day and one of the major figures of the movement. By writing formal poetry, he was, in a sense, showing the world that African American writers were as talented as all the white sonneteers (writers of sonnets) throughout history.
Not all the Harlem Renaissance poets felt the same way. Langston Hughes, for example, bucked the system and wrote in free verse and blues forms as an attempt to resist the white culture of poetic tradition. However, Cullen embraced that tradition by writing sonnets but infused them with nontraditional subject matter, like race and religion. He showed the world what should have been obvious already—that black poets are as intelligent and capable as the white poets of the past, but he did so while writing about issues that were contemporary and unique to black culture in America.
In this way, he owned the old school forms with a new school vibe. Cullen's conscious choice to write a sonnet becomes a part of his message. Just like the speaker is asking God why He made a poet black in a world that doesn't respect black poets, Cullen is writing a traditional sonnet to say, "See, black poets are as talented and intelligent as the white poets who came before, so we deserve to be heard." The form becomes the message, and that message is loud and clear.
This matches up with the last two lines of the poem, right? Typically, the last two lines of an English sonnet are considered the volta, and summarize the poem's theme. The volta in "Yet Do I Marvel" marvels at God making "a poet black, and bid him sing." Likewise, Cullen is a black, Harlem Renaissance poet writing a sonnet (sonnet means "little song"), so take that, poetry establishment.