In the book 1984 by George Orwell, one of the party slogans is, "Who controls the past controls the future; who controls the present controls the past."
What idea of the novel is directly illustrated by the slogan?
The phrase "Who controls the past controls the future; who controls the present controls the past," in 1984 by George Orwell exemplifies the author's understanding of totalitarianism as based on controlling how and of what people can think just as much as limiting their freedom of action. If people are constantly fed misinformation, and have no idea of other ways of living, they have no models on which to base or concrete goals for a rebellion against a totalitarian political system.
In 1984, Winston, the protagonist, is engaged in rewriting history. So that people will not protest a reduction in food rations, his organization rewrites all available texts to make it appear that food rations were lower in the past than they actually were, making the current reduction appear to be an increase. Similarly, to preserve the party's aura of omniscience, if a spokesperson's predictions do not prove true, they are rewritten.
The idea is based on the actual practice of the Soviet Union in Orwell's period and North Korea in the present in which history books were rewritten to justify the acts of current regimes.