At the huge Climate March in New York City in September of 2014, I spotted a child—perhaps a girl, perhaps a boy—perched on her father’s shoulders. She stared straight ahead, at the multitude of people in the parade that filled the city street ahead of her. Never before had she seen such a crowd, and now she was right there in the middle of that crowd. And—she must have understood, despite her young age—all of these people had a purpose. As her father had told her, all of these people were demanding a clean and healthy world.