Thoreau, Gandhi, Mandela - it's easy to see why their words and ideas have been massaged into gauzy slogans. They were inspirational figures, dreamers of beautiful dreams. But what goes missing in the slogans is that they were also sober, steely men. Each of them knew that thoroughgoing change, whether personal or social, involves humility and sacrifice, and that the effort to change oneself or the world always exacts a price.