ABSTRACT
This chapter explores some of the basic concepts and procedures in theory construction. Familiarity with the theory construction process is helpful in understanding the condition of a field of scientific inquiry, necessary for doing meaningful research in that field and, indeed, essential for determining whether a field is a science at all. It also argues that more rigorous theorizing would speed up progress in SLA research. Further, it might go some way towards protecting language teachers from seductive but inadequate 'theory based' prescriptions for the classroom. It then describes examples of three major classes of theories in second language acquisition: nativist, environmentalist and inter-actionist theories. The words 'theory' and 'theoretical' evoke a variety of responses in language teaching and research circles for different reasons. For some, the negative response they feel is due to their having sat through conference presentations or read journal articles labelled 'theoretical' which have consisted of a good deal of rhetoric, however eloquent, and very little substance.
