「層次分析」的主要功能是提供研究者相對明確的指引，對左右國家涉外行為的關鍵變數加以釐清和進行分析。然而，理論、分析的層次、議題領域這三者究竟在什麼情況或組合條件下較另一種情況或組合條件會讓一個國關理論相較之下更具解釋力，既有文獻並未提供令人滿意之解答，而是持續在不同的理論或同一種理論內部不同派別之爭辯中呈現一個模糊狀態。本文透過簡易的質性比較分析，將個案依屬性劃分為傳統安全的領土爭端議題，和非傳統安全的經貿糾紛議題，同時將國家彼此間權力的落差大小列入考慮，以期提供較過往研究更為具體明確之解釋。此外，研究結果也發現，強調「偏好」（preference）對國家行為具影響性的理論是研究經貿議題較佳之選擇。惟本文也同時指出，小國的國內政治往往僅能解釋自己特定的涉外行為，但無法左右大國的外交政策；相較之下，大國的國內政治，特別是其國內層次中的「偏好」，具有相當準確的解釋和預測效果，不但能協助研究者掌握大國涉外行為之變化，也可以解釋對小國外交政策的影響。

The primary function of Level-of-Analysis is to provide IR scholars with relatively clear guidelines to clarify and analyze the key variables that affect foreign policies decided by states. However, current literature is unable to offer a satisfying answer to under what circumstances or in what way the combination arranged between theories, level-of-analysis, and issue areas that empowers an IR theory with more explanatory power. Instead, it remains obscure during the debates among different IR theories or among different schools within a theory. Through qualitative comparative analysis (QCA) as a method, this article categorizes the case of territorial contestation as a traditional security issue and the case of trade dispute as a non-traditional security issue based on their attributes. Furthermore, the differences between states in terms of power are taken into consideration. By doing so, this article contributes some explanations that are more specific and more precise than those of the existing studies. The research finding shows that theory which emphasizes impacts of preference on states’ foreign policies is a better option for studying issues about economy and trade. It also points out that the domestic politics of small states can only be able to explain their own certain foreign policies but unable to affect great powers’ foreign policies. By contrast, the domestic politics of great powers, especially their preferences at domestic level, provide relatively accurate explanations and predictability. Namely, not only can they help IR scholars get a better picture of great powers’ foreign policy behavior, they can also explain the impact of great powers’ foreign policies on small states.