巴特第二版《羅馬書釋義》（以下作《羅 II》）於 1922 年出版時，即因嚴肅挑戰了當時德語神學的主流範式而成為時代經典。關於《羅 II》的二手文獻可謂汗牛充棟，其中不乏探討其辯證法的著作；巴特筆下「不可能的可能性」之辯證，亦吸引了許多學者的注意，特別是其於《教會教理學》(Die Kirchliche Dogmatik) III/3當中所扮演的角色。然而，此辯證在《羅 II》中的功用，在德語及英語學界卻幾乎被完全忽略。本文旨在闡述可能性與不可能性之辯證之於《羅 II》的重要性，顯示其為貫穿該著作的核心主題，支撐整部釋義的神學架構。巴特這套取自聖經的辯證，與長十九世紀 (Long Nineteenth Century) 的哲學與神學進行對話與辯論，交織成複雜的神學架構。本文文末從《羅 II》文本的詮釋轉移至巴特後期神學的發展，探討巴特於《教會教理學》III/3重拾「不可能的可能性」之辯證後，如何用它來平衡他基督中心本體論當中的救恩論客觀主義傾向，以避免「基督一元論」的聯想與指控。簡言之，若欲明白《羅 II》在巴特整體神學發展當中的獨特性，掌握「不可能的可能性」之辯證在這部著作當中的核心意義，乃不容忽視的關鍵。

The second edition of Karl Barth’s Epistle to the Romans (henceforth Romans II) became an epoch-making classic upon its publication in 1922 by issuing a serious challenge to the reigning paradigm in German theology at the time. Existing secondary literature on Romans II easily fills a bookshelf or two, and many authors have chosen to focus on the dialectics featured in this commentary. Barth’s impossible-possibility dialectic in Church Dogmatics III/3 has also attracted much scholarly attention. However, the use of this dialectic in Romans II has curiously remained a mostly untapped aspect of his writings in both German and English Barth studies. The aim of this article is to demonstrate the significance of the dialectic between possibility and impossibility in Romans II by arguing that it undergirds the central themes of the opus and provides a framework that supports the entire commentary. This dialectic, originally drawn from scripture, encompasses a robust dialogue with philosophical and theological viewpoints from the Long Nineteenth Century. The final section of this article shifts its focus from the text of Romans II to Barth’s theological developments thereafter, examining the re-emergence of the long-abandoned impossible-possibility dialectic Church Dogmatics III/3 to balance the soteriological objectivism of his mature doctrine of election in an attempt to avoid the “christomonist” overtones of which his christocentric ontology has been accused. In a word, to appreciate the uniqueness of Romans II in the successive stages of Barth’s theological development, the significance of the impossible-possibility dialectic cannot be overstated.