Editor's Summary: Individual behavior impacts the environment, but what impacts individual behavior? Effective laws and regulations, strong financial incentives and penalties, social pressure, and the like leave little room for personal values to influence behavior. It is only when these contextual influences are weak that personal factors are likely to play a larger role. Paul Stern therefore argues that the best way to change behavior depends on the behavior and its context and that interventions in the context are more effective than targeting individuals directly with verbal appeals, information, or other efforts to change attitudes or beliefs. And because a variety of factors influence behavior, creative approaches involving multiple influences on behavior offer the greatest potential for change.