國際關係建構主義學者內部不同知識論的爭論或焦慮，尤其是現代建構主義與後現代建構主義的知識論爭議，因為後者根本反對有共同知識論與方法論的存在，影響了建構主義內部的建橋計畫，乃至整個國際關係理論建橋計畫的可能性，更明確地說，國際關係理論的綜合是否可能呢?遂有必要更為細緻與詳細的探討不同建構主義學者個別的觀點，藉以呈現國際關係理論研究的複雜性、多元性。本文以 Alexander Wendt、Jeffrey Checkel、Emanuel Adler 和 David Campbell 等建構主義學者作為範例探討建構主義內部的知識論與方法論爭議，Wendt 與 Checkel 是科學實存論的現代建構主義，Adler 是 務實實存論的現代建構主義，Campbell 是反實存論後現代建構主義，四人在知識論與方法論上的主張，正可以呈現出建構主義內部的知識論爭論，並簡介建構主義常用的研究方法，以說明建構主義的多元方法論，作為觀察國際關係理論綜合的基準與評論基礎。

The different epistemological assumptions or anxieties among constructivists, particularly, the epistemological debate between modernistic constructivists and postmodernistic constructivists, and it may not only have a profound impact on the bridge building project within constructivism but also on the bridge building projects in the International Relations Theory (IRT). Clearly and namely, can it be possible for the synthesis of IRT? It is necessary to conduct a more sophisticated and detailed research on constructivism’s epistemological assumptions to demonstrate the complexities and diversities in IRT.

This paper takes some leading constructivists - Alexander Wendt, Jeffrey T. Checkel, Emanuel Adler, and David Campbell - as examples to study the epistemological debates within constructivism. Wendt and Checkel both are modernistic constructivists, Campbell is a postmodernistic constructivist, and Adler is in the middle. I will use their different epistemological assumptions as an observation and evaluation to check the synthesis of IRT.