Like Sibyls of the future; they have power— The tyranny of pleasure and of pain; They make us what we were not—what they will, And shake us with the vision that's gone by,[36] The dread of vanished shadows—Are they so? Is not the past all shadow?—What are they? Creations of the mind?—The mind can make Substance, and people planets of its own20[34] 20 [34] With beings brighter than have been, and give A breath to forms which can outlive all flesh.[37] I would recall a vision which I dreamed Perchance in sleep—for in itself a thought, A slumbering thought, is capable of years, And curdles a long life into one hour.[38] II. I saw two beings in the hues of youth Standing upon a hill, a gentle hill, Green and of mild declivity, the last