"Proem" is about poetry, so its big-deal, major theme is Language and Communication. This is about how poems are written, what they have the power to do, and the words and sounds that they're made up of. (By the way, this kind of poetry-about-itself is called "metapoetry.") Just how to know that a poem is a poem, and just what a poem is capable of, are some of the major goals of this imaginative investigation. Sort of like CSI-Poetry!
It's natural, baby. In "Proem," language is made out to be a living, breathing thing, and poetry is therefore a natural occurrence, not an artificial creation.
Let's break it down. Even though syllables contain no meaning (most of the time) in and of themselves, they are the basic building blocks for a poem.