This study is an attempt to understand SLA studies by sketching a partial history of the field with a specific focus on the tension between cognitive and social worldviews in SLA studies. In the 1990s, this tension was revealed by two controversies between SLA researchers advocating a cognitive orientation and their critics. The first controversy was about what an SLA theory should look like—the "theory construction debate"—and the second controversy was on fundamental assumptions held and concepts used in mainstream SLA— the "cognitive-social debate." I argue that while the theory construction debate reveals the presence of scientism in SLA studies, the cognitive-social debate indicates the cognitivism in the field. This present study is a historical account of these two debates.