In Nineteen Eighty-Four there’s scene in which Winston Smith ponders the purpose of his job which is to rewrite historical documents. He asks ‘I understand HOW: I do not understand WHY.
He wondered, as he had many times wondered before, whether he himself was a lunatic. Perhaps a lunatic was simply a minority of one. As one time it had been a sign of madness to believe the earth goes round the sun: today, to believe that the past is unalterable. He might be alone in holding that belief, and if alone, then a lunatic. But the thought of being a lunatic did not greatly trouble him: the horror was that he might also be wrong.
Totalitarianism can do many things. It can lock people up. It can make them believe 2 + 2 = 5 (as Winston writes in the dust on the table at the Chestnut Tree café at the end of the novel). And it can make people believe they’re ‘a minority of one’. In Nineteen Eight-Four it’s ‘a sign of madness’ to think as Winston does (until he is tortured into thinking something else) that ‘the past is unalterable’.