For, after all, how do we know that two and two make four? Or that the force of gravity works? Or that the past is unchangeable? If both the past and the external world exist only in the mind, and if the mind itself is controllable – what then?

George Orwell

1984. Part 1, Chapter 7. The thoughts of Winston, who works for the Ministry of Truth, where he alters the historical record to match the Party’s propaganda. Welcome to the world of official deception, surveillance, and manipulation of history by a totalitarian state.