許多研究指出英文寫作教學應著重學生的推理和批判性思維技能，而非只強調英文語法、中英翻譯、和段落寫作。但多數英文寫作教學仍注重寫作技巧本身而忽略思辨的重要性。因此本研究旨在探討如何運用辯論的方式，幫助提升學生英文論說文寫作與批判性思維技能。受測對象為大學英語寫作課程的學生。這些學生在受測期間交替成為對照組和辯論組。資料收集包括學生於受測前、後撰寫的論說文、線上辯論內容、問卷調查和訪談。分析架構以 Anderson 等人 (2001) 所提出的教育分類法為基礎，並採用內容分析法來評估學生的批判性思維技能。研究結果顯示，辯論有助於學生理解使用佐證資料的重要性，擴展他們的思維視角，並增加撰寫英文論說文的信心。此外，辯論組比對照組學生更能展現他們的批判思維能力。具體來說，在寫作時，辯論組學生比控制組學生出現較多具批判思維的句子，且辯論組學生在完成辯論任務後寫的文章字數也較控制組學生多。此結果顯示辯論活動對辯論組學生有正面的刺激與影響。本文末提出對未來英語寫作教學與相關活動設計的建議。

Researchers have argued that, in addition to grammar, translation, and paragraphing, students’ reasoning and critical thinking skills should be emphasized when teaching English as a foreign language (EFL) writing. Studies have indicated that asynchronous debate is effective and self-paced in terms of fostering students’ thinking skills due to its asynchronous nature. The purpose of this study was therefore to examine whether and how asynchronous debate could help enhance EFL students’ critical thinking skills in two EFL courses. The students in both classes took turns being in the conventional and debate conditions. The data sources included drafts and revisions, online statements, perceptual surveys, and interviews. Content analysis was used to assess the students’ thinking levels based on the educational taxonomy framework proposed by Anderson et al. (2001). The findings reveal that the students, overall, had positive perceptions of the debate activities. Debating helped them understand the importance of evidence in constructing arguments, broaden their thinking, and gain confidence in composing essays. The students in the debate condition improved their thinking skills more than those in the conventional condition. Nonetheless, a similar improvement did not exist when they were switched to the conventional condition in the second round of writing. Pedagogical implications are also provided.