In 1984, "Doublethink" is reality control: the power to hold two completely contradictory beliefs in one's mind simultaneously. It's a kind of paradox, a conscious lie, by the government: the ultimate form of propaganda.
That was the ultimate subtlety: consciously to induce unconsciousness, and then, once again, to become unconscious of the act of hypnosis you had just performed. Even to understand the word ’doublethink’ involved the use of doublethink.
The best examples are, of course, the mottoes of the dystopia:
War is peace. Freedom is slavery. Ignorance is strength.
These are used by the Ministry of Truth to condition and indoctrinate the masses. By keeping the proles uninformed, they are more easy to control. By telling them lies, the Party enslaves them in disinformation, quelling their ability to organize and rebel.
If you look at any commercial on TV, you'll see the same conscious lies: "Our product is the best!"; "100% satisfaction guaranteed"; "The customer is always right." Also, look at the military, churches, political campaigns, and cable news channels: they spread doublethink with the best of them.
Doublethink is sort of the foundation of the society the Winston Smith is living in in this book. It is the idea that a person can have two kinds of thought in their head at the same time. These are thoughts that cannot possibly both be true. The two truths cancel each other out. But the person who is doing doublethink is able to hold both of those "truths" in their mind at the same time even though they are completely contradictory. Here is how the book puts it -- doublethink is
To know and not to know, to be conscious of complete truthfulness while telling carefully constructed lies, to hold simultaneously two opinions which cancelled out, knowing them to be contradictory and believing in both of them...
This is really very hard to get your brain around. To me, it is almost like being insane.
According to the novel, doublethink is:“ To know and not to know, to be conscious of complete truthfulness while telling carefully constructed lies, to hold simultaneously two opinions which cancelled out, knowing them to be contradictory and believing in both of them, to use logic against logic, to repudiate morality while laying claim to it, to believe that democracy was impossible and that the Party was the guardian of democracy, to forget, whatever it was necessary to forget, then to draw it back into memory again at the moment when it was needed, and then promptly to forget it again, and above all, to apply the same process to the process itself -- that was the ultimate subtlety; consciously to induce unconsciousness, and then, once again, to become unconscious of the act of hypnosis you had just performed. Even to understand the word 'doublethink' involved the use of doublethink.. ” “
The power of holding two contradictory beliefs in one's mind simultaneously, and accepting both of them....To tell deliberate lies while genuinely believing in them, to forget any fact that has become inconvenient, and then, when it becomes necessary again, to draw it back from oblivion for just so long as it is needed, to deny the existence of objective reality and all the while to take account of the reality which one denies — all this is indispensably necessary. Even in using the word doublethink it is necessary to exercise doublethink. For by using the word one admits that one is tampering with reality; by a fresh act of doublethink one erases this knowledge; and so on indefinitely, with the lie always one leap ahead of the truth.