Three categories of tension are identified as potential correspondents of psychological forces: tension arising from own needs, from induced needs, from the need to satisfy impersonal demands. To these, a fourth is added in which tensions are coordinated to someone else's desire to locomote toward or away from a region in his life space. From this Lewinian perspective, altruism and other less dramatic forms of prosocial behavior are part of a general theoretical question: What conditions determine whether individuals develop tension systems coordinated to another's goal attainment? The process by which tension is coordinated to another person's goal attainment is here called promotive tension arousal. Conditions that determine whether promotive tension arousal produces behavior that facilitates or hinders another's goal attainment are discussed.