In Japanese, there are two kinds of forms which stand for epistemic modality(EM) : one type 'daroo' can be used in questions, and the other-so-called secondary modal forms(e. g. 'kamoshirenai')-can not.This paper explains this phenomenon and analyzes the meaning and function of 'daroo' in relation to a new discourse model in Japanese.
EM implies that the contradictory assumption is also probable in the supposed world. On the other hand, a typical question stands for the optional relation of the supposed worlds. Because of this relation, the secondary modal forms can not be used in questions. For example, a collocation such as *kare-wa tabun ichinensei kamoshirenaika ?(Lit.Possibly, may he be a freshman?) is ungrammatical.
'Daroo' however can be used in. quetions. The meaning of 'daroo'should be regarded as the indicator of judgement-forming process(IJFP)in discourse. In questions, 'daroo' functions as the moderation of the demand for a clear answer. In declarative sentences, 'daroo' means possibility, in case the hearer's information is neglected, but- if the hearer's information is mentioned, 'daroo' means a sort of confirmation. These phenomena can be explained if we assume that IJFP can involve the hearer's judgement in the discourse, and these arguments are supported by morphological evidence.