“This book will change your sense of how grand the sweep of human history could be, where you fit into it, and how much you could do to change it for the better. It's as simple, and as ambitious, as that.”—Ezra KleinAn Oxford philosopher makes the case for “longtermism” — that positively influencing the long-term future is a key moral priority of our time. The fate of the world is in our hands. Humanity’s written history spans only five thousand years. Our yet-unwritten futur