Chierchia's (1998a, 1998b) theory of the Nominal Mapping Parameter classifies languages into three categories on the basis of its bare nominal semantics. With this mapping, he claims that the type of nominal in every language should fall into one of the three categories in his model. Chierchia further suggests that the presence of classifiers is associated with the absence of a semantically active and obligatory plural morpheme in classifier languages (i.e. [+arg,-pred] languages). However, this seems not to be the case for Indonesian as a classifier language since its plural morphology is both syntactically and semantically active. This book discusses the behavior of Indonesian classifiers and plurals with regard to the discussion of Chierchia's model. In the end, it is obvious that Indonesian is a classifier language, yet its plural morphology has the same characteristics as those non-classifier languages. For this reason, Indonesian is called as a language which has a "dual system".