From Orwell Today:
The day-to-day falsification of the past, carried out by the Ministry of Truth, is as necessary to the stability of the regime as the work of repression and espionage carried out by the Ministry of Love. The mutability of the past is the central tenet of Ingsoc. Past events, it is argued have no objective existence, but survive only in written records and human memories. The past is whatever the records and the memories agree upon. And since the Party is in full control of all records and in equally full control of the minds of its members, it follows that the past is whatever the Party chooses to make it. As often happens, the same event has to be altered out of recognition several times in the course of a year. At all times the Party is in possession of absolute truth. To make sure that all written records agree with the orthodoxy of the moment is merely a mechanical act.
The alteration of the past is necessary for two reasons. To be able to learn from the past meant having a fairly accurate idea of what had happened in the past. One reason is that the Party member, like the proletarian, tolerates present-day conditions partly because he has no standards of comparison. He must be cut off from the past, just as he must be cut off from foreign countries, because it is necessary for him to believe that he is better off than his ancestors and that the average level of material comfort is constantly rising.
But by far the more important reason for the re adjustment of the past is the need to safeguard the infallibility of the Party. It is not merely that speeches, statistics, and records of every kind must be constantly brought up to date in order to show that the predictions of the Party were in all cases right. It is also that no change in doctrine or in political alignment can ever be admitted. For to change one's mind, or even one's policy, is a confession of weakness.
Source: https://www.orwelltoday.com/past.shtml
Thank you for grokking, Walleye: The truth matters for democratic government as lies matter for tyrannical government.