One of the fundamental causes of the divisions between Christians is individualism. True unity is impossible where each person thinks of himself as his own ultimate ecclesial authority. Moreover, as I argued here, any non-sacramental grounding of ecclesial authority is intrinsically individualistic. Therefore true unity is impossible where Christians believe that the essence of the grounding of ecclesial authority is non-sacramental. The reunion of all Christians depends upon recognizing that sacramentality is the true grounding of ecclesial authority.
I have argued here that the Montanist, Novatian and Donatist schisms erred precisely in failing to recognize sacramentality as the true grounding of ecclesial authority. I have also argued here that Protestantism does not have sacramentally grounded ecclesial authority; Luther and Calvin redefined 'apostolic succession' as formal agreement with the Apostles, rejecting the Catholic doctrine that Apostolic succession is essentially sacramental.
I noticed that Sean Michael Lucas has recently stated that apostolic succession is essentially doctrinal, not sacramental. He writes, "For Protestants, the means for unity is also apostolic succession, but it is a succession of commitment to the apostolic message and mission."
Defining "apostolic succession" as fundamentally non-sacramental entails individualism. And individualism is intrinsically opposed to unity. So Lucas has adopted as a means to unity a position that is intrinsically opposed to unity. The question that those holding a doctrinally-grounded conception of ecclesial authority overlook is: Whose determination of doctrinal apostolicity is authoritative? Without sacramentality, the answer is ultimately either "My own" or "No one's" (which is functionally equivalent to "My own"). In other words, wherever sacramentality is not recognized as the essence of apostolic succession, we are left with individualism.
Lucas adds: "As the authority of Word and Spirit continues to be observed in Protestant churches, we manifest the unity of Christ's church even in the midst of our denominational groupings."
Lucas seems to think that the present state of denominational fragmentation in Protestantism manifests the sort of unity Christ desires for His followers, simply because Protestants "observe the authority of Word and Spirit". It would seem then that for Lucas, schism does not detract from the unity of the Church so long as the schismatic parties continue to "observe the authority of Word and Spirit". But the claim to be "observing the authority of Word and Spirit" would apply to all the early heresies, as St. Vincent of Lerins points out. If the Protestant denominations are truly "observing the authority of Word and Spirit", then why are the Word and Spirit saying so many incompatible things, that the various Protestant denominations cannot be united into one denomination? Should we believe that the Word and Spirit are contradicting themselves, or should we believe that some people are misinterpreting the Word and misunderstanding the Spirit?
The unity that Christ desires His followers to have is not merely the shared desire to follow the Word and the Spirit. Even tritheists could affirm that sort of ecclesial unity. Christ desires that His followers be one, even as He and the Father are one. And the Father and the Son are one in Being, not merely in desire, and not merely in intention. Christ therefore desires that His followers be fully incorporated into one Body, as I have argued here and here. If God hates divorce, man separating what God has joined together, then how much more does God hate schism, when men rend His Bride? We must not delude ourselves into calling evil "good", or division "unity". When we start to allow ourselves to see the fragmented state of Protestantism for what it is, instead of pretending that it manifests the unity of Christ's Church, then like Cindy Beck and Kristine Franklin, we start to see the necessity of sacramentally grounded ecclesial authority, and the path to true unity, i.e. being fully incorporated into one Body.
"Let unity, the greatest good of all goods, be your preoccupation." - St. Ignatius of Antioch (Letter to St. Polycarp)