A broad consensus exists that the use of appropriate methods are important in the Scholarship of Teaching and Learning. However, methodological controversies arise around what constitutes acceptable evidence, if one needs a control group, how generalizable results must be, and other similar issues. Much SoTL work, I argue, asks questions about how much a particular treatment (innovation) caused an effect (student learning), and how the results found in one particular context can be extended outside that context (generalizability). These concepts, known as internal validity and external validity, respectively, provide a common point of departure for much scholarship on teaching and learning. This paper addresses these concepts and demonstrates how they can unite much of what divides us within the methodological realm of SoTL.