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.