Our adult concept of choice is not a simple idea, but rather a complex set of beliefs about the causes of actions. These beliefs are situation-, individual- and culture-dependent, and are thus likely constructed through social learning. This chapter takes a rational constructivist approach to examining the development of a concept of choice in young children. Initially, infants' combine assumptions of rational agency with their capacity for statistical inference to reason about alternative possibilities for, and constraints on, action. Preschoolers' build on this basic understanding by integrating domain-specific causal knowledge of physical, biological, and psychological possibility into their appraisal of their own and others' ability to choose. However, preschoolers continue to view both psychological and social motivations as constraints on choice--for example, stating that one cannot choose to harm another, or to act against personal desires. It is not until later that children share the adult belief that choice mediates between conflicting motivations for action. The chapter concludes by suggesting avenues for future research--to better characterize conceptual changes in beliefs about choice, and to understand how such beliefs arise from children's everyday experiences.