I looked at him, holding my head in my hands. “I couldn’t swear that I understand that,” I said slowly. “And I repeat, that it looks like lifting yourself by your own bootstraps.” The homely simile did not dismay him. He pointed a finger at me as he spoke: “You’ve seen a chip of wood bobbing on the ripples of a pond. Now you think the chip is moving; now the water. Yet neither is moving; the only motion is of an abstract thing called a wave. “You’ve seen those ‘illusion’ diagrams, for instance this one of a group of cubes. (Diagram is on opposite page.) Make up your mind that you are looking down upon their upper surfaces, and indeed they seem below you. Now change your mind, and imagine that you are down below, looking up. Behold, you see their lower surfaces; you are indeed below them. You have ‘gone somewhere,’ yet there has been no translation of anything. You have merely changed coordinates.” [Illustration: _Make up your mind that you are looking down upon the upper surfaces of the cubes, and indeed they seem below you. Now change your mind, and imagine that you are looking up. Behold, you see their lower surfaces._] “Which do you think will drive me insane more quickly--if you _show_ me what you mean, or if you keep on talking without showing me?” “I’ll try to show you. There are some types of mind, you know, that cannot grasp the idea of relativity. It isn’t the mathematics involved that matters; it’s just the inability of some types of mental organization to grasp the fact that the mind of the observer endows his environment with certain properties which have no absolute existence. Thus, when you walk through the garden at night the moon floats from one tree top to another. Is your mind good enough to invert this: make the moon stand still and let the trees move backwards. Can you do that? If so, you can ‘go somewhere’ into another dimension.” * * * * * Woleshensky rose and walked to the window. His office was an appropriate setting for such a modern discussion as was ours; situated in a new, ultramodern building on the University campus, the varnish glossy, the walls clean, the books neatly arranged behind clean glass, the desk in most orderly array; the office was just as precise and modern and wonderful as the mind of its occupant. “When do you want to go?” he asked. “Now!”