Kenneth Minogue (1930-2013) Politics: A Very Short Introduction (1995)

Chapter 8. The Experience of Politics: I. How to be an Activist
...Politicians train for the real world by endless talk about past landmarks and present possibilities, and they do so in a special language of their own. Thus ‘appeasement’ is no longer in politics the name of a type of response to someone’s discontent, but refers to a dispute about foreign policy in the 1930s. For several decades after the Second World War it denoted an episode of shame and cowardice. Then came revision, an attack on the reputation of Churchill, the great critic of appeasement, and the argument that Britain’s lone stand against Hitler in 1940 had merely delivered her into the hands of the rising empires of the USA and the USSR. It is very seldom that events stand still for long, and the paradox is that the past is nearly as opaque as the future.
...As Harry S. Truman remarked: ‘About the biggest power the President has is the power to persuade people to do what they ought to do without having to be persuaded.’