趙紫宸對於傳統新教倫理提出挑戰，他對於人因信稱義而無須自我努力就可以成能道德的義的這種可能性提出質疑。他個人的解答是信徒與基督合一，這便造就了基督與信徒問在道德上的合力同工，以致於基督與信徒一同行動。細讀羅馬書第六章後，發現經文部分支持趙紫宸的倫理神祕主義，但也顯示了趙紫宸和保羅之問巨大的差距。雖然保羅要求信徒與基督合一，並且是一種充滿倫理意涵的合一，但是他不像趙紫宸對於培養道德生命的可能性看得那麼樂觀。趙紫宸向某些西方的保羅學者（史懷哲、布特曼、陶德、凱士民、費茲麥爾）看齊，嘗試要在羅馬書中為倫理奠定穩固的神學基礎，但是他們的嘗試都受到挫折。失敗的根本原因在於：保羅在羅馬書中關切的不是想要建構一個道德體系，而是與自己同胞爭論猶太人的身分問題，亦即羅馬書第六章所涉及到的切身問題：強調恩典是否會會導致猶太人民族意識的失落？假設律法的核心地位失落了，猶太人的身分還有什麼優勢呢？那麼，我們是否會活在「罪中」，落在上帝盟約應許之外？保羅和他的對手在意的不是德行的陶成或自我圓滿，乃是猶太人身分的失落。

Zhao Zichen issues a challenge to traditional Protestant ethics by questioning the possibility of accomplishing moral righteousness as a result of faith (因信稱義) without self-effort. His own solution is an identification with Christ that creates a moral synergy between Christ and believer, so that as Christ acts the believer also acts. An exegetical examination of Romans 6 yields support for Zhao's ethical mysticism but also reveals profound differences from Paul. While Paul does call for identification with Christ and imbues it with ethical implications, he is less optimistic than Zhao in the possibility of cultivating a moral life. Zhao joins a host of Western interpreters of Paul (Schweitzer, Bultmann, Dodd, Käsemann, Fitzmyer) in their frustrated attempts to find in Romans a firm theological foundation for ethics. The root cause for the failure is that in Romans Paul is concerned less with constructing an ethical system than with engaging in an intramural debate about Jewish identity with his Jewish interlocutors. Romans 6 is concerned with the question of Jewish identity. Is grace stressed at the expense of Jewish ethnicity? If the centrality of the Torah is compromised, what advantage does the Jewish identity have? Will we then live ＜||＞in sin＜||＞-that is, outside God's covenantal promise? Both Paul and his detractors are concerned much more with the loss of Jewish identity than with virtue-building or self-perfection.