Here is part of the argument and imagery of Four Quartets. First there is the argument by Bergsonian, Christian and Indian mystics alike that the moment of illumination reveals (as in Plato's metaphor of the cave) the distinction between reality and its mere shadow. The sunlight fills the empty pool; presence is overcome by absence; meaning seems to be revealed. Then there is Eliot's reservation about the Platonic language of light and shadow, for, given the values of light and shadow defined in the early essay, one finds a significant ambiguity in this mystical moment of illumination in 'Burnt Norton'. It is not clear what has been revealed, what truth it is that humankind cannot bear. Is the light (presumably the light of the Gospel of John that becomes the Word by the end of this poem) real, marking all else as merely shadow? Or is shadow real (the darkness that comes with the cloud), marking the momentary light as merely an illusion? It is not clear which of these phenomena the bird is calling 'reality'. The ambiguity is no accident; it comes from Eliot's disenchantment with the 'meretricious captivation' of this sort of 'promise of immortality' that he had encountered in Bergsonism. His fear was that the inner light was no more trustworthy than the inner voice, I which breathes the eternal message of vanity, fear, and lust.' As always, the test is pragmatic; these moments 'can be judged only by their fruits.'
And yet pragmatism is no simple alternative to this mystical moment, Bergsonian or otherwise. One therefore also finds in 'Burnt Norton' the twenty-year fear of pragmatism's replacement of the spiritual part of our diet by fiction. The mysterious, lyrical fourth section of the poem focuses upon this fruitless option. The puzzling rhetorical questions serve to mock the pragmatic proposition that reality is a function of human need. The passing away of the sun (as in the first section of the poem, symbolically the reality outside the human being) exposes the ludicrousness of the suggestion that we could replace the sun: 'Will the sunflower turn to us, will the clematis / Stray down, bend to us: tendril and spray / Clutch and cling?' How can the world's being depend on human being? This section of the poem ironically reverses the bird's claim that humankind cannot bear very much reality: it is no longer to bear reality in the sense of 'to endure' reality; it is to bear reality in the sense of 'to sustain, support, create' reality.
From "Risking Enchantment: The Middle Way between Mysticism and Pragmatism in Four Quartets." In Words in Time: New Essays on Eliot’s Four Quartets. Ed. Edward Lobb. Ann Arbor: University of Michigan Press, 1993.