I have seen the worst of humanity. I led a nation through a war where brothers killed brothers. And yet I tell you: I believe in the better angels of our nature. Not because people are always good — they plainly are not — but because believing in their potential for goodness makes them more likely to reach it. When you expect the worst, you often receive it. When you appeal to what is noble in someone, you give them something to rise toward. This is not naivety; it is strategy for a better world.