After some research and because this poem seems so inaccessible, here are a few ideas about its makeup: The poems in this series, including "The Lost Son" are psychological comparisons, similar to what the German poets used to call a "bildungsroman" but also quite different because the poems don't show a linear progression from innocence to ethical strength. Also relative to the psychological factor is this quote from "Madness in the New Poetry" by Peter Davison..."Is madness a conflict between imagination and reality? (Theodore Roethke would call it "nobility of soul at odds with circumstance.") Perhaps, but what else but that very conflict gives rise to poetry? Where madness enters in we may expect incoherence; but let us take care to discriminate between the incoherence of not knowing how, and the incoherence of reaching beyond. Madness without poetry can sometimes, through the excitement that rises from it, arouse in the reader feelings much like those that would be aroused by poetry without madness. Longinus defined the difference as between the sublime and the beautiful; but twentieth-century psychiatric madness has all too little of the sublime about it. Where it engages the poet too closely with himself it tends to damage poetry, for the self should be the reservoir of poetry rather than its shallop. Poetry has suffered long from the preponderance of the idea that it exists to scratch the poet's itch. When madness enters in, the poet may try to cure himself upon the page, or to drive himself on to further intoxications of madness. If madness damages poetry, poetry must be defended. The poet as poet bears responsibility for the excellence and wholeness of his poem more than for his self's wholeness, no matter how mad he happens to be. In examining some of the books of verse published in the last year, I have kept in mind poetry before madness. Let us watch the outcome of each struggle."
http://www.theatlantic.com/issues/65jan/davison.htm