What s Grammatical in Grammaticalization?

The scope of research in grammaticalization has been among the controversial topics in recent grammaticalization scholarship, since it is tied to the question of what is grammaticalization. In the heart of the controversy is the different conceptualization of the concept of grammar and grammaticality , because grammaticalization, per se, is procedural, involving acquisition of or increase in grammaticality, or the characteristics of grammar. Despite the fact that there are innumerable instances of linguistic change that may be unequivocally labeled as grammaticalization, there are also a large number of linguistic changes that lie in the borderline, whose statuses in terms of grammaticalization entirely depend on the definition of grammar. This paper presents the controversy in several categories; proposes that certain changes that may fall outside the traditional conceptualization of grammaticalization may still have to be addressed in the grammaticalization studies. It proposes that the significant changes of linguistic forms that are grammatical either as a source or a target do not violate the unidirectionality should be considered as instances of grammaticalization, and that the widely-accepted principles of grammaticalization including unidirectionality should be not diagnostic principles but heuristic principles. This paper further identifies the remaining issues that call for clarification of the diverse notions surrounding grammaticalization.