Of all the particles in Japanese, the dative particle ni is perhaps the one whose meaning is most difficult to pin down. It denotes, among many other things, location, goal, source, cause, purpose, reason, recipient, giver, causee, passive agent, and even experiencer in dative-experiencer-subject constructions. Some of its meanings, such as goal/source, reason/purpose,and recipient/giver, are semantically the polar opposites of one another. In this in-depth study of the particle, Hansen maintains that the syncretism exhibited by the dative case marker in Japanese is not arbitrary, but the result of meaning extensions of the two basic senses: goal and location. Moreover she argues that it was not the meanings of the dative as such that were extended, but that of entire constructions containing the dative. To explain the mechanisms behind the extensions the author draws upon the theoretical frameworks of Cognitive Grammar and Construction Grammar with additional support from typological and diachronic studies.