The Ministry of Truth is part of the main theme of the novel concerning the nature of language and history. Orwell believes that truth and free speech are the enemies of totalitarianism and that one of the essential steps in establishing totalitarian government is taking control of language, truth, and memory. The Ministry of Truth, which could more accurately be termed one of Propaganda or even mind-control via language, is engaged in several crucial projects for doing this.

The Ministry is engaged in creation of a new language called Newspeak which makes it impossible to articulate subversive thoughts. Another branch of the Ministry is responsible for creating entertainment. Another major function of the Ministry, for which Winston is partly responsible, is rewriting history to make it consistent with present ideology and policy. This means, for example, the Winston goes back through earlier newspapers to revise inaccurate predictions and make them coincide with what has actually happened.

The Ministry of Truth is actually the ministry of lies, just as the Ministry of Love is actually the ministry of torture. At the Ministry of Truth, history is rewritten to align with whatever is the current Party orthodoxy, and it is also where propaganda is produced. Winston's job is to rewrite newspaper articles to align with the Party's current version of reality. For example, whatever superpower Oceania is at war with is supposed to be the superpower it has always been at war with, so when the enemy changes, Winston has to alter newspaper articles to make it appears that Oceania has always been at war with this enemy. He also has to alter news stories to erase Party members who have fallen into disfavor. When he has produced the new version of reality, he drops the old news story down the memory hole where it is burned in a furnace. He then performs doublethink to forget that he ever altered anything, though Winston is prone to commit such thoughcrimes as remembering.