Paul was eight hundred feet above the world's fastest river, balancing one foot on a steel wire half an inch in diameter. His mouth was a hard line, and his jaw was clenched. His arms projected from his sides, tensed and motionless. The trick was to think of nothing but the rope, and not even the rope but the place where it touched his flesh. He cleared his mind like a physicist clearing a blackboard, with sharp, fast strokes. His head buzzed with the strain that results from reducing a nervous system to two square inches of skin. The wind blew past his cheek, and he shifted his balance slightly.
He received the sum of his training, his instincts, and his conscious knowledge in the form of an emotion which told him that the wind and the barely perceptible vibration of the wire were perfect. He gave his will the one outlet that would not destroy him, and it shot down his leg like compressed steam. He ran. He occupied his mind with one muscle at a time in a fixed sequence, dimly aware that his survival was balanced on his ability to make that sequence an absolute. He did not have to know the world or the position of his body, so long as foot followed foot and his limbs' thrusts were straight along the line. A part of him that he was not watching relaxed, because Paul was capable of certainty and knew that these motions would carry him to the end.