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.