在聖經的啟示中，聖三與基督的存在形態主要是不斷地外展、虛己或去中心化（decentralization）。這是教會外展使命的根源。教會的存在形態本應是聖三與基督之存在形態的外顯和在歷史中的延續。但事實卻不常如此，與此形態不盡一致，甚至相反的情況，即便在今天，也依然在教會內存在，即自我中心化。這種形態嚴重阻礙教會在福傳使命中的自我實現。為此，教會需要改革。教宗方濟各沿著梵二的路線所給出的改革方向與方案是共議同行。本文主要探討共議同行一方面如何透過整合教會之所是與教會之所行，更新對教會的理解，另一方面如何具體地使教會更加符合聖三與基督去中心化的面貌，即實現其使命性的存在本質。

In biblical revelation, the Holy Trinity and Christ’s mode of existence primarily are characterized by continuous outgoing movement, self-emptying (kenosis), or decentralization. This dynamic forms the foundation of the Church’s missionary outreach. The Church’s very nature should manifest and historically continue the mode of existence of the Trinity and Christ. Yet, this is often not the case. Even today, forms that are inconsistent with or opposed to this nature persist within the Church, such as self-centeredness. This attitude severely hinders the Church’s self-realization in her mission of evangelization. Therefore, the Church needs to be reformed. Following the path of Vatican II, Pope Francis proposes synodality as the direction and solution for this reform. This article primarily explores how synodality, on the one hand, renews our understanding of the Church by integrating what the Church is with what the Church does, and on the other hand, concretely enables the Church to more closely resemble the decentralized nature of the Holy Trinity and Christ—that is, to realize its essential missional existence.