The most serious long-term threat facing the world is the danger that human actions are producing irreversible, harmful changes to the environmental conditions that support life on Earth. If this problem is not overcome, there may be no viable world for our descendants to inhabit. Because this threat is caused by human population growth, overconsumption, and lack of resource conservation, social scientists have a vital role in helping our world escape ecological disaster and approach a sustainable level of impact on the environment--one that can be maintained indefinitely. Enormous changes to human lifestyles and cultural practices may be required to reach this goal. This article discusses major obstacles to this goal, describes a variety of motivational approaches toward reaching it, and proposes that we should view the achievement of sustainable living patterns as a superordinate goal--a war against the common enemy of an uninhabitable world.