The earth cannot support humanity’s increasing population and consumption. Concerned scientists and citizens are therefore wondering how we might work toward a sustainable, survivable human future. Sustainability involves increased technological efficiency and agricultural productivity, but also incentives and attitudes that moderate consumption. Social psychology contributes to changing attitudes and behavior with evidence that a) materialism exacts psychic as well as environmental costs, and b) economic growth has failed to improve human morale. Two principles–the adaptation level phenomenon and social comparison–help explain why materialism and increasing affluence fail to satisfy.