This study is a theoretical reflection on the relationships between the ASEAN Community and an East Asian community envisioned by the East Asia Vision Group (EAVGⅠ) and proposed by the EAVGⅡ to be launched in 2020 as the East Asia Economic Community. It is based on the eclectic perspective of ``middle-ground constructivism``, focusing on interaction between material and ideational factors, on one hand, and between static structures and dynamic processes, on the other. While independent variables include political power in realism, economic interest in liberalism and cultural identity in constructivism, dependent variables, i.e. the relationships between the two communities, encompass ``monistic expansion`` in constructivism, ``dualistic interdependence`` in liberalism, and ``pluralistic competition`` in realism. It is concluded that their ultimate relationships will be shaped in the intersubjective political process of regionalism, which actively construct, as well as passively reflect, the interdependent economic structure of regionalization.