Transcending the Trade-off Between External and Internal Validity: A Critical Realist Perspective

This article contributes to the mixed methods literature by proposing a critical realist philosophy of science to resolve the apparent, and ultimately unfruitful, trade-off between internal and external validity. It is argued that this trade-off is a false dichotomy rooted in contestable philosophical assumptions about causality. Thanks to its stratified ontology and epistemological focus on causal mechanisms, critical realism allows for reconceptualizing internal and external validity as interdependent components of explanatory adequacy. Identifying causal mechanisms is a prerequisite for understanding the scope conditions under which those mechanisms operate. Testing these scope conditions, in turn, strengthens confidence in the initial explanation. The article thus provides mixed methods research with a philosophical foundation for an integrated understanding of validity.