Proselytism has become a ＂hot issue＂ in discussions about the unification of the church and missiology. The decline of the traditional denominations is an important topic that the churches have to face. Basically the definition and interpretation of this topic come mainly from the more traditional, received and historical denominations because they come to be aware of the crises they face, namely that their ＂orthodoxy＂ is declining with the rapid growth of younger churches. Therefore, the younger ones become target of condemnation by the traditional ones. How shall the mainline churches and their theologies face this ＂post-denominational＂ age is the context to be treated seriously. The paper begins with a treatment of the Lutheran theologian Paul Tillich. The dialectic between potentiality and realization in a spiritual community brings out movement as the nature of the church. On the other hand, the paper starts with Calvin's Reformed thinking of church and faith community and reflects upon the growing movement of denominational believers in light of transcendental election. It then tries to give some theological reflections upon both the traditional denominations and the emerging churches that attract the movement of youths.