The idea that people inevitably act in accordance with their self-interest on the basis of a calculation of costs and benefits does not constitute an adequate framework for understanding political acts of violence and self-sacrifice. Recent research suggests that a better understanding is needed of how sacred values and notions of self and group identity lead people to act in terms of principles rather than prospects when the two come into conflict. Perhaps the greatest challenge is to better understand how sacred causes and moral imperatives diffuse through a population and motivate some (usually small) segment of it to commit violent actions. The challenge to psychology is to adopt an interdisciplinary focus drawing on a range of research methods and to become bolder in its choices of study populations if it is to be relevant to real-world problems. (Contains 1 table, 1 figure and 1 footnote.)