"Keats mourned that the rainbow, which as a boy had been for him a magic thing, had lost its glory because the physicists had found it resulted merely from the refraction of the sunlight by the raindrops. Yet knowledge of its causation could not spoil the rainbow for me. I am sure that it is not given to man to be omniscient. There will always be something left to know, something to excite the imagination of the poet and those attuned to the great world in which they live (p. 64)"

Source: Robert Frost, Lawrance Roger Thompson (1964). “Selected letters”