回顧歷來的「以文為詩」說，無論持贊同或反對意見，還是試圖調和二者，都各自擁有對文體「本質」的想像，以致爭論難解。對於宋人而言，文體越界似成為普遍之創作現象，然而是否意味著文體出現了「應有」的新型態？本文則以此為切入點，嘗試採用詩文並讀、同題互見的分析角度，從歐陽脩、蘇軾的創作實踐中，釐清他們對於「文體越界」的真實表現。在「同題」的詩、文中作家各有側重，有其「寫」與「不寫」之考量，創作上儘管有「越界」的因子，但最終仍是回歸各自的書寫傳統。因此，「以文為詩」作為宋人「出位」的藝術表徵應有所調整，因為在書寫上看似「破體」的表現，其實皆有創作脈絡可循，或可謂其書寫本身即是一種延續並創造傳統的實踐。

The idea of ＂using prose in poetry＂ 以文為詩 down the ages, whether one agrees or disagrees with it, is in the end an attempt to reconcile the two literary forms. Each has its own conception of the essence of literary form, leading to unresolvable differences of opinion. In the Song dynasty, writing across the boundaries between forms seemingly became a common phenomenon. But does this imply the appearance of a new ＂proper＂ style in literary forms? Taking this question as its entry point, this article attempts to clarify when Ouyang Xiu's and Su Shi's writing really crossed the boundaries of literary forms. The approach taken is to read both poetry and prose side by side, comparing and contrasting works on the same theme. When writing poetry and prose on the same theme, each writer has his own emphases and considerations of what to write and what not to write. Even though crossing literary boundaries is a factor in their writing, in the end each writer reverts to his own writing tradition. The view of Song writers' use of prose in poetry as a sign of breaking through artistic limitations therefore requires to be questioned, because what looks like ＂breaking the form＂ in their writing, can in fact be traced back along a line of creative tradition. Perhaps it could be said that the practice of such writing is a continuation and creation of tradition.