The Menace From Earth ssc by Robert A. Heinlein

lead blindly irked him. "I'm from Missouri," he said. "I'll see for myself." He moved toward the Gate.
    "Where are you going?"
    "Through! I'm going to look up Diktor and have it out with him."
    "Don't!" the other said. "Maybe we can break the chain even now." Wilson felt and looked stubborn. The other sighed. "Go ahead," he surrendered. "It's your funeral. I wash my hands of you."
    Wilson paused as he was about to step through the Gate. "It is, eh? H-m-m-m — how can it be   my   funeral unless it's   your   funeral, too?"
    The other man looked blank, then an expression of apprehension raced over his face. That was the last Wilson saw of him as he stepped through.
    -
    The Hall of the Gate was empty of other occupants when Bob Wilson came through on the other side. He looked for his hat, but did not find it, then stepped around back of the raised platform, seeking the exit he remembered. He nearly bumped into Diktor.
    "Ah, there you are!" the older man greeted him. "Fine! Fine! Now there is just one more little thing to take care of, then we will be all squared away. I must say I am pleased with you, Bob, very pleased indeed."
    "Oh, you are, are you?" Bob faced him truculently. "Well, it's too bad I can't say the same about you! I'm not a damn bit pleased. What was the idea of shoving me into that ... that daisy chain without warning me? What's the meaning of all this nonsense? Why didn't you warn me?"
    "Easy, easy," said the older man, "don't get excited. Tell the truth now — if I had told you that you were going back to meet yourself face to face, would you have believed me? Come now, 'fess up."
    Wilson admitted that he would not have believed it.
    "Well, then," Diktor continued with a shrug, "there was no point in me telling you, was there? If I had told you, you would not have believed me, which is another way of saying that you would have believed false data. Is it not better to be in ignorance than to believe falsely?"
    "I suppose so, but —"
    "Wait! I did not intentionally deceive you. I did not deceive you at all. But had I told you the full truth, you would have been deceived because you would have rejected the truth. It was better for you to learn the truth with your own eyes. Otherwise —"
    "Wait a minute! Wait a minute!" Wilson cut in. "You're getting me all tangled up. I'm willing t'o let bygones be bygones, if you'll come clean with me. Why did you send me back at all?"
    "'Let bygones be bygones,'" Diktor repeated. "Ah, if we only could! But we can't. That's why I sent you back — in order that you might come through the Gate in the first place."
    "Huh? Wait a minute — I already   had   come through the Gate."
    Diktor shook his head. "Had you, now? Think a moment. When you got back into your own time and your own place you found your earlier self there, didn't you?"
    "Mmmm — yes."
    " He — your earlier self — had not yet been through the Gate, had he?"
    "No. I —"
    "How could you have   been   through the Gate, unless you persuaded him to   go   through the Gate?"
    Bob Wilson's head was beginning to whirl. He was beginning to wonder who did what to whom and who got paid. "But that's impossible! You are telling me that I did something because I was going to do something."
    "Well, didn't you? You were there."
    "No, I didn't — no ... well, maybe I did, but it didn't   feel   like it."
    "Why should you expect it to? It was something totally new to your experience."
    'But ... but —" Wilson took a deep breath and got control of himself. Then he reached back into his academic philosophical concepts and produced the notion he had been struggling to express. "It denies all reasonable theories of causation. You would have me believe that causation can be completely circular. I went through because I came back from going through to persuade myself to go through. That's silly."
    "Well, didn't you?"
    Wilson did not have an answer ready for that one. Diktor continued with, "Don't worry about it.