"Physical control is not enough. With you there would have to be mental control as well. Unfortunately you radiate much more strongly than your fellow men, and we are unable to shut you out without exerting considerable effort that could better be employed elsewhere." The alien eyed Matson speculatively. "There you go again," he said. "Now you're angry." Matson tried to force his mind to utter blankness, and the alien smiled at him. "It does some good--but not much," he said. "Conscious control is never perfect." "Well then, what can I do?" "Go away. Your range fortunately is short." Matson looked at the alien. "Not yet," he said coldly. "I'm still looking for something." "Our technology," Ixtl nodded. "I know. However I can assure you it will be of no help to you. You simply do not have the necessary background. Our science is based upon a completely different philosophy from yours." To Matson the terms were contradictory. "Not as much as you think," Ixtl continued imperturbably. "As you will find out, I was speaking quite precisely." He paused and eyed Matson thoughtfully. "It seems as though the only way to remove your disturbing presence is to show you that our technology is of no help to you. I will make a bargain with you. We shall show you our machines, and in return you will stop harassing us. We will do all in our power to make you understand; but whether you do or do not, you will promise to leave and allow us to continue our studies in peace. Is that agreeable?" Matson swallowed the lump in his throat. Here it was--handed to him on a silver platter--and suddenly he wasn't sure that he wanted it! "It is," he said. After all, it was all he could expect. They met that night at the spaceship. The aliens, tall, calm and cool; Matson stocky, heavy-set and sweating. The contrast was infernally sharp, Matson thought. It was as if a primitive savage were meeting a group of nuclear physicists at Los Alamos. For some unknown reason he felt ashamed that he had forced these people to his wishes. But the aliens were pleasant about it. They took the imposition in their usual friendly way. "Now," Ixtl said. "Exactly what do you want to see--to know?" "First of all, what is the principle of your space drive?" "There are two," the alien said. "The drive that moves this ship in normal space time is derived from Lurgil's Fourth Order equations concerning the release of subatomic energy in a restricted space time continuum. Now don't protest! I know you know nothing of Lurgil, nor of Fourth Order equations. And while I can show you the mathematics, I'm afraid they will be of little help. You see, our Fourth Order is based upon a process which you would call Psychomathematics and that is something I am sure you have not yet achieved." Matson shook his head. "I never heard of it," he admitted.