The orthodoxies of the past didn't change, or at least didn't change
rapidly. In mediaeval Europe the Church dictated what you could
believe, but at least it allowed you to retain the same beliefs from
birth to death. It didn't tell you to believe one thing on Monday and
another on Tuesday....
Now, with totalitarianism exactly the opposite is true. The
peculiarity of the totalitarian state is that though it controls
thought, it doesn't fix it. It sets up unquestionable dogmas and it
alters them from day to day. It needs the dogmas because it needs
absolute obedience from its subjects, but it can't avoid the changes,
which are dictated by the needs of power politics. It declares itself
infallible, and at the same time it attacks the very concept of
objective truth.
-- George Orwell. The Complete Works of George Orwell (London: Secker and Warburg, 1998), Vol.12, p.504.