Someone* famously said, “In essentials, unity. In non-essentials, liberty. In all things, charity,” a phrase so famous it’s become known as the Friedensspruch. This mantra has been used by a variety of Christian denominations, most famously with the so-called Christian Irenics after the worst of the Reformation. These people, looking on the relative insignificance of some ugly intra-Christian fighting said, more or less, “Can’t we all get along?” It’s been taken up as a motto by the Disciples of Christ, as well as the Moravian Church of North America and the Evangelical Presbyterian Church, and likely many more denominations, and made its way into Pope John XXIII’s Ad Petri Cathedram. Sometimes, it seems that perhaps the saying itself is the only thing we can all agree upon, but I pray that this Friedensspruch may serve as a catalyst for unity amongst us all, moving forward.
There remains, of course, the issue of who determines which issues are essentials and which are not. I’ve stated before that I don’t think the finer points of justification are very essential; a great many Protestants disagree. The Moravians think that the question of whether Holy Communion consists of the Real Presence of Christ or simply His symbolic presence is a non-essential,** while the Cathechism calls It “the source and summit of the Christian life” (CCC 1324), and the Second Vatican Council calls It “the fount and apex of the whole Christian life” (in the words of Lumen Genitum, 11). Luther held a view of consubstantiation as essential (refusing to negotiate with Zwingli on it), while the Evangelical Lutheran Church of America apparently does not (having altar and pulpit fellowship with the United Methodists, who reject the Lutheran view).
All of this, I believe, draws us to the question of authority: questions regarding the authority of the Bible and its interpretation, questions of the authority of the Church and Her structure, and questions of the authenticity and authority of Tradition. But perhaps the sooner we delve into those questions the better, because whether we recognize it or not, it’s ultimately the issue of the papacy, and papal infallibility, which separates Catholics from non-Catholics.
When the early Church defined Herself as “one Holy, Apostolic, and Catholic Church,” she did not mean simply that she held the Apostolic Faith; She meant that that She was the same Church founded by the Apostles. Someone who happens to agree on every de fide issue that Catholics believe (C.S. Lewis came close) wouldn’t be a full member of the Holy, Apostolic, and Catholic Church without actually joining the physical Church, without acknowledging a human being, the pope, as having earthly, visible headship. This is why even those who believe in Transubstantion generally may not recieve the Eucharist unless they’re formally within Her bounds***, and those who believe in the ability of priests to forgive sins may still (generally) not recieve absolution.
In Protestantism, churches are typically formed on specific doctrinal issues: in other words, the doctrines define the church, rather than the Church defining the doctrines. We Catholics view things very differently. We don’t think of the Church as a set of beliefs. But we also reject the other extreme, that the Church is simply a body of believers without any requisite, unifying belief system. Catholics think of Her as a real, physical entity who holds a specific set of beliefs, yes, but who is more than that; and who is made up of believers, yes, but is more than that. I hope and pray that the Friedensspruch, and other pleas for ecumenism, can draw more Christians to this understanding of who the Bride of Christ is, and why She’s so vital.
*I’ve seen it attributed to St. Augustine, John Wesley, and Rupertus Meldenius. Pope John XXIII left the authorship an open question in Ad Petri Cathedram: “But the common saying, expressed in various ways and attributed to various authors, must be recalled with approval: in essentials, unity; in doubtful matters, liberty; in all things, charity.”
**stating: “In respect to the sacrament of holy communion, the Moravian Church does not try to define the mystery of Christ’s presence in the communion elements, but recognizes that the believer participates in a unique act of covenant with Christ as Savior and with other believers in Christ.”
***At least within the bounds of the Apostolic Church, broadly. So an Eastern Orthodox Chrisitan is permitted to take Eucharist. Also, canon law permits special exceptions, as was apparently done for the late Brother Roger of the ecumenical Taizé Community (it’s a complex tale, but those interested can get the gist here).