"Those of us who are Protestants are tempted to regard the study of Church history as unessential, an extra, perhaps even at odds with our belief in the sufficiency of Scripture. So why pursue it?
The principal reason is because God intends us to learn from the mistakes made and lessons learned by others in the past (Jer. 6:16). It's often been said that those who do not learn from the mistakes of history are doomed to repeat them, and we might be tempted to seize upon this as reason enough for learning about Church history. But there is a more important reason to study Church history: namely, that we’re not cosmic believers in karma but mortal believers in Jesus Christ. We’re responsible not to history but to the Judge of all history. And God has designed His world in such a way that we don't proceed through life simply in a cycle, but rather with the realization that history moves according to His plan, and He intends us to benefit from what Christians in previous eras have done, either rightly or wrongly.
And studying Church history shows us that the Church we see in Scripture didn’t stop there. It didn't exist independently from, or outside of, history, nor did the closing of Scripture's canon mean that the teaching of the apostles stopped with it.
At this point, it is possible for us to fall victim to one of two opposite errors. We might regard the early Church's practice as a) either an unimportant example that can be disregarded, or b) a relic to be slavishly copied. We can see both errors at work in the Church today, sometimes in the same groups.
We see the first error all over the contemporary evangelical world, most notably in the tendency of hip evangelicals to reject practices seen as outmoded, dated, and out of sync with the prevailing postmodern ethos. Fence the Lord's Table from nonbelievers? Disallow women from exercising authority in the Church? Neither of these sits well with evolved progressives who can't allow themselves to be seen in the same light as those primitive leaders of the Early Church.
The second error is one we might be tempted to see only in the Roman Catholic Church. After all, they're the ones concerned about tradition and relics, right? Don't be so sure. Think about it: the same hip emergents who disregard the example of the Early Church's doctrine and practice are often also those most concerned to claim its symbolism and ethos. How often do you hear of churches professing to recover the original essence of Christianity? Of finding again the "real" Jesus? Of creating an authentic "faith community" that fulfills a man's need to be both evolved and moored?
But this tendency isn't limited to emergent churches. Consider any number of "evangelical" churches that desire to tie themselves directly to the Early Church, skipping over 2,000 years of Church history in the process. How about the Campbellites or Restorationists of the Disciples of Christ or other "Christian Church" denominations, who hold the Lord's Supper every week in a haphazard miss-it-and-it's-gone fashion, claiming this to be a restoration of the practice of the Early Church? How about the adherents of Oneness Pentecostalism who excuse their rejection of orthodox Trinitarian doctrine by feigning an adherence to the pure simplicity of the doctrine of the Early Church?
Yet understanding Church history properly shows us that the truth handed down by the apostles (2 Thess. 2:15) continued to guide the church in its first centuries. Errant doctrine crept in, to be sure, but much was preserved by men of God striving to safeguard the good deposit they'd been given. And so, yes, on the one hand we see the error of baptismal regeneration creeping into the Church, but on the other hand we also see the faithful, careful exposition of the doctrine of the Trinity, embryonic in the Early Church, but carefully explained by later generations of faithful pastors. We see that the Christian faith spread worldwide, not simply because of its attractiveness to the poor, as secular scholars opine, but also because of the wise, bold apostolic mission of the Church in the centuries following the apostolic age. Any attempt to be "missional" today without understanding the missionary activity of the historic church is foolhardy and short-sighted.
Much of this myopia in the contemporary church also stems from another trait in our culture: narcissism. Our generation is arguably one of the most self-focused in history, and so it's no surprise that our churches are ever deluded by the mirage of rediscovery, and the allure of self-discovery. When we focus constantly on ourselves, our time, our modern sophistication, our evolved state, it's not long until we become guilty of the arrogance that assumes we can rediscover Jesus, recover original Christianity, or restore the true essence of faith—with no concern for the lessons and discoveries of the past 1,800 years.
It’s here that Church history becomes a great help to us. Understanding Church history shows us that the most incredible, most sophisticated discoveries in the Christian faith were made long ago. It shows us that our great need today is not to let postmodernism inform the doctrine of the Trinity, but rather to proclaim its doctrine, already discovered, to a world that needs old truth explained, not new truth uncovered. Church history shows us that most of the new perspectives we think we've opened today are really little more than rehashing of old heresy. Open theism is nothing more than the posterity of Pelagianism, and its adherents, if more sophisticated, are only the degraded descendents of a man whom St. Augustine defeated 1,600 years ago. Feminism is nothing but ancient goddess worship revived, and abortion nothing but ancient child-slaughter dressed up in American language. And so Church history shows us in detail what we already should have known from Scripture, that there is "nothing new under the sun" (Eccl. 1:9), no temptation but such as is common to man (1 Corinthians 10:13), and that those who ignore the lessons of God’s Church reveal a desire for self-imposed darkness.
But lest I end this brief defense on a negative note, consider also how Church history is a constant testimony to the faithfulness of God among His people. For 1,900 years after the apostles' passing, the Chief Shepherd has safeguarded His sheep, allowing sinful men still to serve as defenders of the truth, and His Church still to show itself as the "pillar and ground of the truth" (1 Timothy 3:15). And so those who ignore this history deprive themselves of the blessings of 2,000 years of God's working in ways that even the Apostles likely never imagined. Upon closing the last book of Scripture, did the Apostle John see how wondrously God would provide for the Church he had served so faithfully? Could he see how it would endure, protected from Arianism, from Pelagianism, from Islam? Could he also see how God would protect it from itself, even? How the innocent purity of the Apostolic message would be corrupted in the coming centuries by sacramentalism, indulgences, and Mariolatry? And how God would use His servants in recovering the truth of the Gospel but without disregarding the truth that had endured?
It's likely John saw none of these things in detail, but it's certain that in our day we can. God has provided us a record of His people's experiences, from Adam to Christ, from Christ to John, and now from John to us today. These things are not just pieces of arcane knowledge; they are records of mistakes made and lessons learned. They are "written for our instruction, upon whom the ends of the ages have come" (1 Corinthians 10:11). God has given them to us as aids to our faith and antidotes to our narcissism, and we disregard them to our own peril and impoverishment. They are not Scripture, but they do show Scripture’s power, and the faithfulness of a God who throughout all time is establishing a Church that the gates of hell will never withstand (Matt. 16:18)."