T.S.Eliot and American Philosophy by Manju Jain, a book found via a Google Book search.
The seven-line snip above is from the middle of the fifth element in the third of Eliot's FOUR QUARTETS, a series of long poems he wrote over a period of seven years. The third "quartet" is titled The Dry Salvages, written in 1941.
Here are words from Jain's book that relate to Eliot and mystical poems, like the one above:
The problem that the rendering of mystical experience in poetry poses for Eliot is that of sincerity, of distinguishing between the genuine and the false, between what one actually experiences and what one would like to experience; and the consequent difficulty of mediating moments that are essentially incommunicable through what he terms ‘the natural sin of language.’ Eliot’s views on the subtle discriminations to be made between the genuine and the false in religious and mystical experience are expressed in his comments on Herbert:And so. It is fair to ask: For all his virtuosity in spinning words into delicious tapestries, are T.S.Eliot's words really just the worst of stinking crap? or an inkling of the sublime brought down to us?
Above that level of attainment of the spiritual life, below which there is no desire to write religious verse, it becomes extremely difficult not to confuse accomplishment with intention, a condition at which one merely aims with the conditions in which one actually lives, what one would be with what one is: and verse which represents only good intentions is worthless – on that plane, indeed, a betrayal. The greater the elevation, the finer becomes the difference between sincerity and insincerity, between the reality and the unattained aspiration.