Incommensurability in Second Language Acquisition Approaches

Researchers in the field of Second Language Acquisition （SLA） have been taking different routes. Some researchers make linguistic-cognitive issues their inquire object and pursue objectivity with quantitative research methods. Other researchers regard the social context of activity as an essential characteristic of learning and teaching. These groups of researchers make use of qualitative research methods like case study, grounded theory, narrative inquiry, and ethnography. There are many other routes that SLA researchers have taken, but the two just mentioned are perhaps the most predominant ones and the ones that are most easily contrasted. The present paper explores the disparity between the different research paths from the perspective of philosophy of science echoing the notion of incommensurability. In this paper the author argues that the differences between different SLA perspectives are not only commensurable but wholesome for the development of SLA.