Economics has provided the most rigorous model of decision making. Unfortunately, its severe rationality assumptions rule out psychological conflict. Modifying the standard model to allow for conflicting preferences creates scope for hesitation, doubt, regret, and akrasia. Akrasia, which is doing wrong knowingly, figures prominently in discussions of morality and justice in classical philosophy. the development of a formal model of akrasia along the lines taken in this essay hols the promise of combining the mathematical rigor of economics, the analytical power of philosophy, and the empirical methods of psychology in the study of justice.