Latin America, North America, Oceania, and southern Africa. But what exactly constitutes Christianity? What does this religion stand for? What makes Christianity Christian? Why have so many people embraced it?
More than one hundred years ago, a professor at a prestigious German university decided to provide answers to all these questions. He arrived at the university lecture hall a few minutes before six o’clock in the morning when it was still dark outside, and the walk across campus had invigorated him. When he stepped up to the podium, not a seat in the house was empty. Six hundred students (all of them male because women would not be admitted to the university until 1908) and a smattering of faculty colleagues had their eyes fixed on him as he began the day’s address. “What is Christianity?” he asked, and they were counting on him to supply an answer. The year was 1900. The place was the University of Berlin. The speaker was Adolph von Harnack, one of the most brilliant and well-known scholars in the world.
Professor Harnack did not disappoint. He gave them a simple and straightforward answer because, he told them, the gospel itself is simple. Christianity at its purest and best is the religion of Jesus, the message that Jesus himself proclaimed. It focuses on three things: the fatherhood of God, the infinite value of the human soul, and the commandment to love everyone. In a nutshell, that was it. That is the essence of Christianity. Christians had advocated many other beliefs and practices during the movement’s long history, but, according to Harnack, those other things were largely superfluous. The only thing that really matters is Jesus’s core teaching. This is the gospel – the message Christianity has to share with the world – and that gospel (or “good news”) is simple.
Something even more basic was at stake, however. For Harnack, the simple gospel of Jesus is not merely the essence of Christianity, it is the quintessence of religion itself. A humanistic scholar who affirmed the validity of science, Harnack served as the first president of the Kaiser Wilhelm society which later became the Max Planck Society for the Advancement of Science, one of the most prestigious centers for the study of human evolution in the world. Harnack was interested in human origins, and he believed that it is religion – the spiritual impulse that leads people to wonder about the mystery of life and how they are called to live – that makes Homo sapiens into something more than merely smart animals. For Harnack, a proper understanding of the gospel of Jesus was not merely the key to understanding Christianity, it was the key for understanding what makes any of us human. And that is why 600 students voluntarily crowded into a university lecture hall at six o’clock in the morning for fifteen weeks in a row: to hear someone explain who they were called to be as followers of Jesus and who they were as human beings.
The German state church was not impressed with Harnack’s views or erudition. Traditional German Christians thought his interpretation downplayed Christianity’s traditional emphasis on personal salvation and correct doctrine, and they initially tried to block his promotion to the University of Berlin when it was announced in 1888. Ultimately Kaiser Wilhelm II was forced to intervene personally to make sure Harnack got the job. Despite the church’s worries, Harnack himself was deeply committed to Christianity, and his lectures were crafted to provide university students with a positive view of Christianity that was fully compatible with modern learning. He hoped that university students would be so inspired by the message of Jesus that they would leave the university intent on making the German nation a place where “justice is done, no longer by the aid of force, but by free obedience to the good…not by legal regulations but by the ministry of love.”1 He wanted his students, and everyone else who heard or read his lectures, to become better Jesus-following Christians and more intelligent, caring citizens. That is how he envisioned Christianity: as the highest expression of religion itself, a faith focused on goodness and love, and the solution to all of humanity’s problems.
Except it wasn’t. Just a few years after delivering his lectures, Harnack’s own actions undercut his claims. During the early months of World War I, he was one of ninety-three German intellectuals who composed a document entitled “To the Civilized World,” which justified atrocities committed by the German army during its infamous Rape of Belgium. In this statement he and his professorial peers argued that anyone “inciting Mongolians [i.e., Asians] and negroes against the white race, ha[d] no right whatsoever to call themselves upholders of civilization.”2 Harnack may have thought Christianity was the best and most perfect religion for all people, times, and places, but it did not prevent him from rationalizing wanton violence against civilians and championing the cause of German racial supremacy.
Christianity has not been a wellspring of universal goodness for humankind. Christians have contributed much that is good to the world, but they have also done significant harm. They have believed Jesus’s message of love for all people, but have often failed to act in loving, or even decent, ways. And Christianity cannot serve as the sole arbiter of human religiosity. Different religions provide humankind with different visions of the world as it is and could be, they offer different pathways to and definitions of salvation, and they advocate different ideals and values. Christianity is a powerful and inspiring religion, but it is not the simple religion that Harnack described.
In contrast to Harnack’s idealistic portrayal, this book offers a more empirical examination of what Christians have believed, how they have acted, how they have organized themselves, how they have spread their message around the world, and what challenges they are facing today. There is no intention to either criticize or praise the movement; the only goal is fair and accurate description. That said, this book is more than a mere recital of facts and numbers quantifying Christianity from the outside. It also looks at Christianity from the inside, trying to explain Christianity’s spiritual appeal and why so many people around the globe have embraced it.
One obvious fact about Christianity is that it is a far different movement today than it was a century ago when Harnack gave his university lectures. In 1900, two-thirds of the world’s Christians still lived in Europe. Today, only a quarter of the world’s Christians reside in Europe and about 10 percent live in North America. The rest, two-thirds of all the Christians in the world, live in the Global South (Africa, Asia, and Latin America). The internal composition of Christianity has also been transformed. In 1900, three major Christian traditions (Eastern Orthodoxy, Roman Catholicism, and Protestantism) dominated the Christian movement. Now there are four major traditions. The addition is Pentecostalism, and this new tradition, which currently attracts one out of every five Christians globally, has dramatically altered the Christian landscape.3 Simultaneously, the terrain of global politics has been fundamentally reordered. In 1900, half the world’s people were ruled by European colonial governments. Today those former colonies are independent nations, and the Christians who live in them are fully independent of Western Christian control. Christianity is no longer a European religion with a periphery everywhere else; Christianity has become a postcolonial, global faith with many different centers.
This book describes Christianity in eight chapters. Chapter 1 explains how the movement got started, and how within 500 years a small group of followers of Jesus grew into a religion that had a membership that spread across a massive region of the world, ranging from Ireland in the northwest to the southern tip of the Indian subcontinent. Chapter 1 also traces how Christianity changed from a loosely structured and fluid movement into a religion comprised of separately organized and distinct Christian traditions. Today, Christianity is housed in four major traditions – Eastern Orthodoxy, Catholicism, Protestantism, and Pentecostalism – and these four traditions account for about 97 percent of all the Christians in the world. Chapters 2 through 5 explain each of these traditions in turn.
The remainder of the book deals with the characteristics of Christianity as a whole. Chapter 6 describes Christianity’s recent expansion around the world and the changing attitudes of Christians in both the Global North
