Anyone who does manage to disobey the Party is punished and "reeducated" through efficient and cruel torture until one does not know the real truth anymore. By conditioning the minds of their victims with physical torture, the Party is able to control reality, convincing its subjects that 2 + 2 does equal 5. "Freedom is the freedom to say that two plus two make four. If that is granted, all else follows" (81).
The party controls the past by not allowing individuals to keep records of their past, such as photographs or writings of any sort. As a result, memories become fuzzy and unreliable, and citizens become perfectly willing to believe whatever the Party tells them. By controlling the present, the Party is able to manipulate the past. And in controlling the past, the Party can justify all of its actions in the present.
By means of telescreens and hidden microphones across the city, the Party is able to monitor its members almost all of the time. Also, the Party employs complicated mechanisms to put forth large-scale control on economic production and sources of information, and fearsome machinery to inflict torture upon those it regards as enemies. 1984 reveals that technology, which is generally perceived as working toward the human good, can also facilitate the most wicked evil.
One of Orwell's important messages in 1984 is that language is important to human thought because it structures and limits the ideas that individuals are capable of expressing. If control of language were centralized in a political agency, such an agency could possibly alter the very structure of language to make it impossible to even imagine of disobedient or rebellious thoughts, because there would be no words with which to think them. This idea demonstrates itself in the language of Newspeak, which the Party has introduced to replace English. The Party is constantly refining and perfecting Newspeak, with the ultimate goal that no one will be capable of conceiving anything that might question the Party's absolute power.