The flame, white now, had come to rest in the middle of the rocky floor. Even as he stooped, it rose to meet him, winking out--and there rested lightly on his palm the gray sphere, cool and unsmirched, that he had tossed away a few minutes before. But it was no longer a detached, external object. It was part of him, responsive to his every mood and thought, linked to his mind by tracts that were invisible but as real as the nerves connecting mind with muscle and sense organ. It was not a machine, telepathically controlled. It was a second body. Relief, stark wonder, and exulting awareness of power made him weak. For a moment everything swam and darkened, but only for a moment--he seemed to suck limitless vitality from the thing. He felt a surge of creativeness, so intense as to be painful, like a flame in the brain. He could do anything he wanted to, go anywhere he wanted to, make anything he wanted to, create life, change the world, destroy it if he so willed-- And then--fear. Fear that, since the thing obeyed his thoughts, it would also obey his foolish, ignorant, or destructive ones. People can't control their thoughts for very long. Even sane individuals often think of murder, of catastrophes, of suicide-- Suddenly the sphere had become a gray globe of menace. And then--after all, he couldn't do _anything_. Besides any other limitations the thing might have, it was certainly limited by his thoughts. It couldn't do things he didn't really understand--like building a subtronic engine-- Or-- For the first time since he had emerged from the tunnel, he tried to think collectedly, with more than the surface of his mind. He found that the depths of his mind were strangely altered. His subconscious was no longer an opaque and impenetrable screen. He could see through it, as through a shadowy corridor, sink into it, hear the thoughts on the other side, the thoughts of the other Thorns. One of them, he realized, was instructing him, laying a duty upon him. The message dealt with such matters as to make the imagination shiver. It seemed to engulf his personality, his consciousness. His last glimpse of World III was a gray one of dark, snow-streaked pines wavering in a rocky frame. Then that had clouded over, vanished, and he was in a limitless blackness where none of the senses worked and where only thought--itself become a sense--had power. It was an utterly alien darkness without real up or down, or this way or that, or any normal spatial properties. It seemed that every point was adjacent to every other point, and so infinity was everywhere, and all paths led everywhere, and only thought could impose order or differentiate. And the darkness was not that of lightlessness, but of thought itself--fluttering with ghostly visions, aflash with insight.