Book excerpt: The first 2 volumes of Roger Haight's Christian Community in History received enormous critical attention. Of volume 2, a reviewer in the Anglican Theological Review wrote: "This work is worthy of celebration...anyone who cares about the theology of the church must read it." Those volumes of Christian Community in History described the historical diversity of the church across its history (up to the Reformation in vol. 1) and among the churches (since the Reformation in vol. 2). By contrast, vol. 3 is an attempt to describe what the churches possess in common, i.e., to retrieve ecclesiological constants from history reaching back to scriptural origins in order to construct and portray the common ecclesial existence shared by the churches. In more traditional terms, it aims to find the apostolicity, the catholicity, and the unity amidst the plurality of the churches.