The Nightmarish Opposite of Doubt

The best lack all conviction, while the worst
Are full of passionate intensity.

From Bertrand Russell's "Mortals and others":

"The moral of this story is that believers in every kind of ‘ism’ ought to hang together, however opposite their nostrums may be. They differ from ordinary people by the fact that they have a nostrum. One man’s nostrum is only endurable to the ordinary person when it is counterbalanced by another man’s nostrum. If the believers in any one ‘ism’ could convert the believers in all other ‘isms’ to their way of thinking the general run of mankind would find them so boring that they would exterminate them. This applies to the believers in optimism no less than it applies to the believers in pessimism. The pessimism of our age is generally explained as being due to the bad state of the world, but I believe it is quite as much due to the boredom, which we all endured in youth through the optimism of the Victorians."

From Roger Scruton's "The Uses of pessimism":

"The worst are precisely those who wish to sweep away the settled community of strangers, and to impose in its place either a divinely ordered 'brotherhood', or the conscripted unity of a society at war. The best are those who are no more convinced about anything, than they are convinced that convictions should not matter. Robespierre, Lenin, Hitler, Sartre, Mao and Bin Laden do not share many features. But they are united in one thing, which is the 'passionate intensity' that comes from demanding conviction and unity in the place of settlement and doubt."