I have a confession to make: I like the Mercersburg theologians, too. That may sound strange coming from someone who spends his time thinking and writing about 19th and 20th century southern Presbyterians, but while I was at seminary, I spent a great deal of time reading John Williamson Nevin and Phillip Schaff. And the reason I did was because I was attracted to their vision of "reformed catholicism."
After all, I was raised in a church context that started Plymouth Brethren, moved to a Bible church, and then ended up Independent Baptist (and other variations from there). Particularly for the Brethren and for non-denominational Bible church types, there is an underlying desire for Christians to lay aside their "distinctiveness" in order to be "mere Christians" around the common table of the Lord. The problem was that by not having a creed, there was an unwritten creed of which folks inevitably ran afoul--dispensational premillennialism; separatism; legalism.
By the time I got to seminary, I longed for something that emphasized the larger unity of Christ's church on the one hand (in ways similar to my upbringing) while making explicit our creedal and confessional commitments. That was the major reason I found Nevin such invigorating reading--staunchly Reformed and yet desirous to explore the larger "catholic" reality of the church. Over time I was able to read Nevin both sympathetically and critically--sympathetic to his vision, critical of the intellectual and ecclesial means by which he tried to accomplish it. Especially important in this regard was paying attention to his context and not being tempted to divorce him from it.
And yet, I've never truly given up on the ideas on catholicity which he articulated. For example, one of my first full length essays in the WTJ was on "J. Gresham Machen, Ned B. Stonehouse, and the Quandary of Reformed Ecumencity": how do Reformed churches affirm their own doctrinal commitments on the one hand while working together with other Reformed and non-Reformed churches? While I wasn't fully satisfied with the answers that some gave (esp. Van Til), I felt the pressure--from my past and hopes for the future--to explore these issues. And even after I became Presbyterian, I never saw myself or acted in ways that were "sectarian."
I say all that to set forth my bona fides on this issue. Because at the end off the day, I worry that what I mean by "Reformed Catholicism" and what others may mean represent two different things.
What I mean probably would be better covered by the other label: Reformed Catholicity. That is, from the profound embrace and understanding of our own unique Presbyterian identity, we engage other Gospel-oriented traditions with charity and respect, hoping that we may be mutually encouraged (Romans 1:12) as a result of the exchange.
What I fear that others mean by this label: from the discomfort with and lack of understanding of our own unique Presbyterian identity, we adopt beliefs and practices from other Christian traditions (including, especially, Roman Catholicism) in ways that transform Presbyterianism into something that looks a whole lot like Anglicanism, Lutheranism, or Roman Catholicism.
I'll be quite candid--I don't want to mess with the boundaries what we have typically understood (and what I have tried to represent in On Being Presbyterian) as "plain ol' Presbyterianism." And in saying that, I recognize that this Presbyterian identity needs to be incarnated within our own, unique, contemporary cultural systems, which may cause our beliefs and practices to look different from the 17th or 19th centuries (in the same way that these beliefs and practices will look differently in Japan as opposed to the US). Still, if Reformed Catholicism means that we are drawing beliefs and practices from other, "higher church" traditions to meld with our own, then ultimately we are looking to forge something other than Presbyterianism.
Along that line, it is striking that those who promote "Reformed Catholicism" are only looking to the "high church" or mainline American Protestant traditions to demonstrate their catholicity. And yet, the fastest growing form of Christianity is actually Pentecostalism--for example, there are over 220 million Assemblies of God adherents worldwide. What does Reformed Catholicism look like in the face of global Pentecostalism? It doesn't appear that advocates are interested discussing that question.
And yet, I think the pose of "Reformed Catholicity" actually helps us to do so--because it starts with understanding, affirming, and embracing our own religious identity (our beliefs, practices, and stories). And then, from that starting place of self-understanding, it moves to engage others not to adapt and adopt the best of their tradition nor to paternalistically impart our greater "wisdom." Rather, I seek to keep the main thing the main thing--seeing the radical Gospel orientation and common faith in Jesus, I engage in charitable and humble conversation and cooperation when possible to live out the primary reality that we both share--we are both clothed with Jesus Christ by faith alone in him.
Thus, perhaps we would be better served to think more intentionally about what we mean by "catholicism" in the language we use. If we mean simply a reformed version of Roman Catholicism, we don't need to seek that because it already exists--it is called Anglicanism. But if we mean an affirmation of our common union in Jesus with others who do not share our Presbyterian and Reformed identity and of our desire to dialogue with them with charity and great respect, then perhaps we should think about "Reformed Catholicity" instead.
And it may be that it is in this way, out of our own sense of who we are as Presbyterians, that we are "catholics" after all.