"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?"
This proves the amount of control and regulation they had over reality. The citizens were being brainwashed, leaving resistance or disagreeing as no longer an option. They were constantly under surveillance by the government. The citizens were not aloud to think for themselves, or have a mind of their own.