本文以「邊緣性」(marginality)的概念，詮釋小國愛沙尼亞(Estonia)的安全政策。「邊緣性」兼具地緣政治、認同、權力關係等多重意涵，適合用以探討小國的安全政策。從此觀點來看，位居邊緣位置的小國，不必然總是受制於中心或大國主導的秩序;由於前者本身是構成秩序的一部分，它也具有影響中心的可能性。後冷戰時期的愛沙尼亞，在外交與安全政策上可說由俄羅斯轉向西方。在這個置換中心的過程中，它一方面向新的中心(北約與歐盟)表達向心力，積極參與其主導的秩序，另一方面也藉由強調其特殊性，而影響北約與歐盟對俄羅斯與其他後蘇聯時期國家的政策。儘管有這些正面的事例，愛沙尼亞的策略卻也有其限制，例如它的觀點與批判，最終無法影響德國與俄羅斯主導的天然氣管線計畫。中心與邊緣的關係，因而是動態且有不同可能性的。

This paper attempts to (re)interpret Estonia’s security policy by adopting the concept of “marginality,” an idea that bears such elements as geopolitics, identity, size and power relations, and is therefore suitable for studying small states’ security policies. A small state located at the margin is not necessarily constrained by or subjected to the great power at the center, because as a constituent part of the very relationship, the margin always has certain potential to exert influence on the center. In the case of post-Cold War Estonia, the state has undergone a reorientation of foreign and security policy away from Russia and towards the West. In this process of “center- substitution,” Estonia has shown a great commitment to the new center by actively taking part in the order(s) constructed by the NATO (the United States in particular) and the EU. In addition, through exploiting its marginal position between Russia and the West, Estonia also seeks to shape the attitude of the NATO and EU towards the old center, Russia, and other post- Soviet states. Despite these positive practices, there are also limits to Estonia’s room of maneuver. An example in this regard can be found in Estonia’s failed attempts to overturn the “Nord Stream” gas pipeline project conducted and promoted by Germany and Russia. The relationships between a center and a margin therefore are dynamic and can have various outcomes.