It's increasingly common to come across evangelicals who've convert to Eastern Orthodoxy and Roman Catholicism (some might even be part of one of your favourite bands or a classmate). Many have conducted rigorous and prayerful investigations into the depths of the Christian tradition and have become convicted and convinced that they must leave behind their Protestantism. Testimonies of these intra-Christian conversions abound on Twitter and the blogosphere. Family, friends, and fellow churchgoers may express concern that a loved one or congregant is leaving Methodism or Pentecostalism to swim the Bosporus or the Tiber but the former are often ill-equipped to grapple with church history and arguments based upon tradition and doctrinal development. For evangelical Protestants, the Bible alone is the only infallible authority but this reverence for Scripture has often led to an almost total neglect of other areas of theological authority.

Last year I came across Gavin Ortlund's video ministry. I was impressed with his well-produced videos where he charitably and constructively engaged in intra-Christian apologetics representing a Protestant perspective. I listened to several of his debates and dialogues with apologists of other streams of Christianity such as Trent Horn. Here was an evangelical Protestant who closely examined biblical exegesis, tradition, and church history and could cite church fathers back at detractors of Protestantism. When I learned Gavin was going to be releasing a book that resembled a lot of the content on his TruthUnites channel it became one of my most-anticipated books of the year and it did not disappoint.

'What It Means to be Protestant' is an excellent introduction to what divides Protestantism from Eastern Orthodoxy and Roman Catholicism. Gavin generally builds his arguments based upon the insights of the magisterial Reformation (Luther, Calvin, and John Jewel are cited but the Anabaptists and pentecostals do not make much of an appearance if at all). He also specifically draws inspiration from the Mercersburg theology (he makes the astute observation that it was highly ironic for John Henry Newman to quip that "to be deep in history is to cease to be Protestant" when his contemporary across the Atlantic in America, Philip Schaff, was working on the Nicene and Post-Nicene Fathers collection).

Gavin presents some fairly typical Protestant apologetics such as the scandals and corruptions endemic in the medieval Church and arguments against the papacy alongside a positive championing of "sola Scriptura." One of Gavin's key arguments for Protestantism is that it is the most irenic of the major streams of Christianity. For instance, he conducts two case studies (the Assumption of Mary for Catholicism and the veneration of icons for Orthodoxy) and not only demonstrates how these are later accretions to tradition but also critiques Rome and the East for condemning those who reject these doctrines and practices. Gavin builds his cases based upon recent scholarship (such as Stephen J. Shoemaker's work on the Virgin Mary) as well as on the teachings of the church fathers (who, it turns out, often vigorously disagreed with each other and even contradicted themselves as their thought evolved).

Not that I expect an Orthodox or Catholic Christian to convert to Presbyterianism or Methodism by reading this book but I was surprised that all of the endorsements in the book seemingly come from Protestants; surely an irenic Catholic scholar could have been solicited for a blurb? As well, as I mentioned, this is an introductory book for a wide audience; it is not Stanley Hauerwas and Matthew Levering slugging out esoteric tenets). Still, I think any Christian reader will benefit from this book though I also suspect most of its readership will the "very online" Christian who inhabits Twitter and YouTube. Gavin is irenic and pastoral, cautioning readers to avoid triumphalism, to listen to the best of both sides (i.e. don't let Mark Driscoll and Eric Metaxas represent evangelical Protestantism on the one side and Henri de Lubac and Pope John Paul II represent Rome on the other side) and to deeply and prayerfully reflect if they feel called to change churches.