Harris and Koenig make a compelling case for the importance of adult "testimony" and its influence on children's developing conceptions of topics in science and religion. This commentary considers how their analysis relates to constructivist and sociocultural theories and discusses several ways in which Harris and Koenig's arguments help to debunk some prevalent assumptions about research on the social context of cognitive development. Finally, a number of additional issues are raised for debate and discussion, and some critiques and suggestions for future research are discussed. The issues discussed by Harris and Koenig are crucial if we are to take seriously the importance of culture in cognitive development.