'The Light Falling Down Through the Universe'

I need some help understanding an enigmatic entry the poet Louise Bogan wrote in her journal in 1933:

“Santayana’s classic world – the people in Chekhov ‘seen against the sky’: this is what I knew in childhood and had no word for: this is ‘the light falling down through the universe,’ the look and feeling of which has haunted me for so long –”

Context is no help because there is none. We don’t know what came before or after. The passage is taken from the section titled “Journals and Memoir” in A Poet’s Prose: Selected Writings of Louise Bogan (ed. Mary Kinzie, Swallow Press/Ohio University Press, 2005). It has stuck with me all these years. In the second quoted passage, there’s a sense of exposure and vulnerability. I think of Ezra Pound’s line: “Seek ever to stand in the hard Sophoclean light.” That Bogan should cite two of the writers who mean the most to me is part of the passage’s nagging interest.

First, I think of Chekhov’s long story “The Steppe” (1888), one of his best, about a boy’s journey across the vast Russian steppe in a chaise. The setting sometimes feels like the plains and deserts of the American West – big sky country. One feels exposed, dwarfed, with no place to hide. This is from Constance Garnett’s translation:

“The sun-baked hills, brownish-green and lilac in the distance, with their quiet shadowy tones, the plain with the misty distance and, arched above them, the sky, which seems terribly deep and transparent in the steppes, where there are no woods or high hills, seemed now endless, petrified with dreariness.”

Light – as physics, as metaphor – is everywhere in Santayana’s work. This passage in Obiter Scripta: Lectures, Essays and Reviews (1936) seems pertinent:

“The problem of darkness does not exist in the man gazing at the stars. No doubt the darkness is there, fundamental, pervasive, and unconquerable except at the pinpoints where the stars twinkle, but the problem is not why there is such darkness, but what is the light that breaks through it so remarkably, and granting this light, why we have eyes to see it and hearts to be gladdened by it.”

I don’t quote Chekhov and Santayana (who soon quotes Plotinus) as glosses. Where Bogan writes of being “haunted,” I substitute the persistence of memories. Most of mine include light as an important element – dim or harsh, morning or evening, interior or outside – and different  sorts of light carry various moods. Any insights would be appreciated. Bogan’s passage is not a code to be cracked but a scene to be illuminated.