Free The Menace From Earth ssc by Robert A. Heinlein

guy that the two of you were a trifle closer than twins? "Skip it — you wouldn't know about it."
    "What's your name?"
    "My name? Uh —" Oh, oh! This was going to be sticky! The whole situation was utterly ridiculous. He opened his mouth, tried to form the words "Bob Wilson," then gave up with a feeling of utter futility. Like many a man before him, he found himself forced into a lie because the truth simply would not be believed. "Just call me Joe," he finished lamely.
    He felt suddenly startled at his own words. It was at this point that he realized that he was   in fact,   "Joe," the Joe whom he had encountered once before. That he had landed back in his own room at the very time at which he had ceased working on his thesis he already realized, but he had not had time to think the matter through. Hearing himself refer to himself as Joe slapped him in the face with the realization that this was not simply a similar scene, but the   same   scene he had lived through once before — save that he was living through it from a different viewpoint.
    At least he thought it was the same scene. Did it differ in any respect? He could not be sure as he could not recall, word for word, what the conversation had been.
    For a complete transcript of the scene that lay dormant in his memory he felt willing to pay twenty-five dollars cash, plus sales tax.
    Wait a minute now — he was under no compulsion. He was sure of that. Everything he did and said was the result of his own free will. Even if he couldn't remember the script, there were some things he   knew   "Joe" hadn't said. "Mary had a little lamb," for example. He would recite a nursery rhyme and get off this damned repetitious treadmill. He opened his mouth — "Okay, Joe Whatever-your-name-is," his alter ego remarked, setting down a glass which had contained, until recently, a quarter pint of gin, "trot out that explanation and make it snappy."
    He opened his mouth again to answer the question, then closed it. "Steady, son, steady," he told himself. "You're a free agent. You want to recite a nursery rhyme — go ahead and do it. Don't answer him; go ahead and recite it — and break this vicious circle."
    But under the unfriendly, suspicious eye of the man opposite him he found himself totally unable to recall any nursery rhyme. His mental processes stuck on dead center.
    He capitulated. "I'll do that. That dingus I came through — that's a Time Gate."
    "A what?"
    "A Time Gate. Time flows along side by side on each side —" As he talked he felt sweat breaking out on him; he felt reasonably sure that he was explaining in exactly the same words in which explanation had first been offered to   him.   "— into the future just by stepping through that circle." He stopped and wiped his forehead.
    "Go ahead," said the other implacably. "I'm listening. It's a nice story."
    Bob suddenly wondered if the other man   could   be himself. The stupid arrogant dogmatism of the man's manner infuriated him. All right, all right! He'd show him. He strode suddenly over to the wardrobe, took out his hat and threw it through the Gate.
    His opposite number watched the hat snuff out of existence with expressionless eyes, then stood up and went around in back of the Gate, walking with the careful steps of a man who is a little bit drunk, but determined not to show it. "A neat trick," he applauded, after satisfying himself that the hat was gone, "now I'll thank you to return to me my hat."
    Wilson shook his head. "You can get it for yourself when you pass through," he answered absent mindedly. He was pondering the problem of how many hats there were on the other side of the Gate.
    "Huh?"
    "That's right. Listen —" Wilson did his best to explain persuasively what it was he wanted his earlier   persona   to do. Or rather to cajole. Explanations were out of the question, in any honest sense of the word. He would have preferred attempting to explain tensor calculus to an Australian aborigine,