《文心雕龍‧詮賦》說賦：「述客主以首引，極聲貌以窮文，斯蓋別詩之原始，命賦之厥初也。」強調賦「述客主以首引」的形式，是賦自成文類的重要指標，也是賦之所以為賦的必要條件，可見賦與設辭問對關係之密切。但後來卻不盡如此。設辭問對的賦體是如何發展？其人物如何以從真有其人轉成虛擬主客？後來何以又變成援用歷史人物？風氣如何轉變？轉折是否有其必然性？原是賦最主要特色又何以泯滅？本文即針對這些問題加以探討，試圖從作品與作者、讀者、傳播方式等關係之變動，了解其演變的機制。 本文將賦篇設辭問對大致分四個階段：先秦宮廷暇豫之賦，大多是朝廷口才便給的優者，暇豫侍君戲謔逗趣或迂迴諷諭的對話記錄，是真有其人的言語侍從與帝王的對話，其賦作即使經過整理修飾，仍保留對問體的形式，並以其為大宗。到了西漢，由於宮廷待詔的言語侍從眾多，其賦都是「受詔」而作，賦家是以編寫劇本式的書面創作方式進行，所以需要虛擬人物展開對話。從東漢到六朝，賦家出身與傳播方式變了，賦不再是口誦耳受的聲音藝術，欣賞者直接閱讀書面文字，但賦家仍有採「為主客之分而為對問之體，以曼衍其辭」者，乃藉鬼神或古人代言。但到唐宋賦似乎不再時興出現虛幻的鬼神；也不再時興穿越時空隧道。其設辭問對，乃回歸到西漢以來賦體雜文最單純的作法，設一個不寫名氏的陪襯人物為對話的對象，以肆其發揮而已。

The article divides the assumed dialogues in the form of Fu into four phases. First, before the Chin Dynasty, the assumed dialogues were the real conversation of eloquent actors jokingly satirizing the emperor at leisure, and the Fu, after being arranged and revised, still retained its form of dialogue. Second, in the West Han Dynasty, because of the considerable number of actors, Fu was written in the script form under the emperor’s edict; thus, writers must create characters to develop the dialogue. Third, from the East Han Dynasty to the Six Dynasty, as both the background of the writers and the way to disseminate their works changed, the form of Fu switched from a sound art to a written one. In that period, ancient people and ghosts often spoke in the dialogues. However, the fictitious ghosts and ancient people rarely appeared in the Fu of the Tang Dynasty and the Song Dynasty. Finally, the assumed dialogues returned to the simplest form of composition as that in the West Han Dynasty, that is, to assume an anonymous person to be the conversational partner.