Textual Function of Presupposition in Business Letter Discourse

Presupposition refers to what is assumed by the speaker when uttering a specific sentence, usually realized by the useof particular lexical items and/or linguistic constructions which are known as presupposition triggers, is an evitablerequirement for interpretation of the utterance. Based on the theme-rheme theory and thematic progression patternssuggested by Hu Zhuanglin and Zhu Yongsheng, the author adopts qualitative method to make an analysis of thetextual function of presupposition which is realized by serving as themes in clauses, helping to construct differentthematic progression patterns and transmitting information in business letter discourse. Presupposition helps toconstruct four main thematic progression patterns in business letter discourse, which can be conclude as T1→T2 (thesame theme), R1→R2 (the same rheme), R1→T2 (the rheme or part of the rheme in the previous clause becomes thetheme of the next clause) and T1+R1=T2 (both the theme and rheme of the preceding clause are encapsulated into anoun phrase functioning as the theme of the frequent clause). The author chose 30 business letters selected from theinternet and several textbooks as the object of research, and they cover almost every stage of foreign trade.