Humanity has reached a critical moment. Our world is unsettled and rapidly changing, and we face existential risks over the next century. Various prospects for the future—good and bad—are possible. Yet our approach to the future is characterized by short-term thinking, polarizing debates, alarmist rhetoric, and pessimism. In this short, exhilarating book, renowned scientist and bestselling author Martin Rees argues that humanity’s future depends on our taking a very different approach to thinking about and planning for tomorrow.