In a world at risk, those attuned to the dangers can feel a powerful temptation to sound apocalyptic alarms to awaken the somnolent. Arousing fear, though, without offering a compelling vision of a better path, awakens only dispiriting anguish and despair. This pessimism is not so much wrong as disempowering. The basis for hope rests on two kinds of arguments, one scientific, the other historical. Quantitative simulation of alternative scenarios shows that sufficient environmental capacity and adequate technical means remain to reach a flourishing planetary civilization. Moreover, the precondition for this Great Transition is found in the shared risks and opportunities an interdependent global system now confronts. In our historical moment, the world has become a single community of fate, the foundation for cultural and institutional transformation. Although catastrophic premonitions cannot be logically refuted, they can be defied in spirit and negated in practice: pragmatic hope is the antidote to dystopian despair.