"You asked me once," said O'Brien, "what was in Room 101. I told you that you knew the answer already. Everyone knows it. The thing that is in Room 101 is the worst thing in the world." (3.5.4, O’Brien)
The cage was nearer; it was closing in. Winston heard a succession of shrill cries which appeared to be occurring in the air above his head. But he fought furiously against his panic. To think, to think, even with a split second left – to think was the only hope. Suddenly the foul musty odor of the brutes struck his nostrils. There was a violent convulsion of nausea inside him, and he almost lost consciousness. Everything had gone black. For an instant he was insane, a screaming animal. Yet he came out of the blackness clutching an idea. There was one and only one way to save himself. He must interpose another human being, the body of another human being, between himself and the rats. (3.5.21)
"Who controls the past controls the future: who controls the present controls the past," repeated Winston obediently.
"Who controls the present controls the past," said O'Brien, nodding his head with slow approval. "Is it your opinion, Winston, that the past has real existence?" (3.2.39-40)