Abstract
It is generally believed that "ru/raru-form" is used only in negative sentences in the classical era, and the usage is expanded to include affirmative sentences in the Middle Ages. This paper explores the history of evolution of usage of "ru/raru-form" as a potential expression in affirmative sentences. This paper argues that "ru/raru-form" can be divided into four types: (I) Individual situations already actualized; (II) Permanent situations; (III) Generality; (IV) Individual situations not actualized. I will show that type (I), (II) and (III) are used for <already achieved potential phrases> before the Middle Ages, and type (IV) appears as <un-realized potential phrases> in the Early Modern. Also, this paper suggests one factor for the appearance of <un-realized potential phrases> is a change in how un-realisted situations are expressed.
