from The Zinn Reader: Writings on Disobedience and Democracy, by Howard Zinn.

Is an optimist necessarily a blithe, slightly sappy whistler in the dark of our time? I am totally confident not that the world will get better, but that only confidence can prevent people from giving up the game before all the cards have been played. The metaphor is deliberate; life is a gamble. Not to play is to foreclose any chance of winning. To play, to act, is to create at least a possibility of changing the world.

What leaps out from the history of the past hundred years is its utter unpredictability. This confounds us, because we are talking about exactly the period when human beings became so ingenious technologically that they could plan and predict the exact time of someone landing on the moon, or walk down the street talking to someone halfway around the Earth.

Who foresaw that, on that day in Montgomery, Alabama, in 1955, when Rosa Parks refused to move from the front of the bus, this would lead to a mass protest of black working people, and a chain of events that would shake the nation, startle the world, and transform the South?