“The Painter” is a rather limited poem, being a sestina, but John Ashbery makes the best of what he is given. Rather than the seemingly nonsensical poems that some of the other authors of sestinas in the anthology produced, this poem is simultaneously firmly grounded in realistic terms and filled with metaphor and allegory. The story itself is rather simple- a painter who wants to paint the sea and is decried by society for it (perhaps referring to Monet?). It is the metaphors contained within the story that make the sestina a complex poem. The most overarching one is most of the poem being used to represent an internal struggle between the individual’s desires and those of society, or perhaps between individualism and collectivism as a whole. But the allegory doesn’t stop there, instead going down another level into the mind of the individual and explaining how he is tortured by this conflict of interests. The poem concludes, rather appropriately, by explaining how the collective mind of society will antagonize this individual and cast him out. But has the individual lost? No, if he already had immersed himself in his subject so thoroughly that it had become his world, he had nothing to lose from being thrown “from the tallest of the buildings”.
Ramblings And Such 
Great comment: you’re absolutely right in pointing out the allegorical nature of “The Painter.” I’m glad you appreciated Ashbery’s sestina. Many consider him to be the greatest living poet in the United States. I was lucky enough to have dinner with him not too long ago. He really has a keen mind and a keen poetic intelligence.