本文主要的目的在於爬梳社會科學方法論中因果機制分析的發展和演進，並進一步評估政治學研究中如何運用因果機制來進行解釋以及討論相關的解釋效力的問題。本文將具體評析政治學國際關係領域中民主和平論之論點，以此來衡量政治學運用因果機制解釋的優勢和侷限。因果機制研究層面上，本文聚焦在機制的定義和類型、機制的觀察性、因果機制與因果關係、法則和中介變數的差異、機制的層次、機制的運作和測量、機制的路徑圖。因果機制運用層面上，本文側重於民主和平論的源起和演進、 民主和平論的重要論述、對於民主和平論的挑戰以及現實主義因果機制的補充解釋。最後，本文針對民主和平論的相關論辯提出因果機制的補充解釋。

The main purpose of this paper is to parse out the development and evolution of causal mechanism and to further evaluate how political research adopts the method of causal mechanism to explain and discuss the explanatory effect in the field of qualitative methods. Our focus is to shed light on the causal mechanism of democratic peace theory in the field of international relations and to gauge its advantages and restraints. On the dimension of causal mechanism, this paper focuses on the definition of mechanism, observation of causal mechanism, the difference between causal mechanism, causality, laws and intervening variables, level of analysis, operationalization and measurement of causal mechanism, and roadmap of causal mechanism. This paper applies the analysis of causal mechanism to the origin and evolution of democratic peace theory, the challenges of realism over democratic peace theory, and the responses from democratic peace theory. Finally, we offer an alternative explanation to the debate between democratic peace theory and realism.