Ehrman points out how extraordinary it was that Christianity started out as a small offshoot of Judaism and became the official religion of the Roman Empire followed by millions of people only a few hundred years later. His aim in this book is to explain how this happened, shifting through naturalistic theories based on the historical evidence, sociology and some psychology. It is often tempting to throw up one’s hands and conclude that we just can’t know anything definite about ancient history, because the evidence is slim and there are always many possible ways to fill in the gaps. But Ehrman presents a plausible case that we can understand the main reasons for the spread of Christianity.

A lot of The Triumph of Christianity is focused on the history of the Roman Empire between the first and fourth centuries. Ehrman spells out the accounts of how Emperor Constantine became a believer in Christianity and favored it in laws. One of the striking parts of the story is that he probably knew very little about the details of the religion, and may well have identified the Christian god with one he already believed in, Sol Invictus. So while he certainly aided the Christian religion, we should be careful about what we mean when we say that Constantine himself was a Christian.

There is some discussion of St Paul and the early Christians, but there’s not much information about how Christianity attracted new converts, so this part of the book is rather short. Ehrman examines texts and suggests that people were impressed by the reported miracles associated with Christianity, but he doesn’t examine so much why they would believe these stories. He does set out suggestions about how Paul travelled to various cities, got a job, went to the synagogue, and preached the new religion to both the Jews and the pagans.

Some of the most interesting work in the book is statistical, computing how many converts it would be necessary to make each decade in order to achieve the growth that it did. Ehrman argues that they only needed to increase the size of their church by about 25-30% each decade, which meant that for each 100 people, they only needed to convert 2 or 3 people each year. All this assumes that people mostly stayed converted after they became Christians, and Ehrman doesn’t address the question of why people didn’t go back to their paganism after trying out Christianity.

Ehrman does emphasize the familiar point that Judaism and Christianity differ from the traditional religious practices in several important respects. First, they demanded belief in just one god, while paganism was polytheistic. It used to be in paganism that people could just add a new god to their collection, but under Christianity, people had to abandon their beliefs in any other gods and reject them as demons. Second, Christianity and Judaism carry with them an ethical system of belief, while paganism was far less focused on ethics. Relatedly, third, Christianity and Judaism were very much systems of beliefs associated with rituals and focused on particular texts, while paganism was much more about the practice of making sacrifices to the gods in order to win their favor, with much more flexibility about what people believed. The exclusivity of Christian belief meant that it tended to edge out pagan religions.

Once Christianity got a strong foothold in the Roman Empire, it also became very intolerant of other religions, and took steps to persecute their followers, destroy or take over their churches and statues. There were many cases of Christians killing pagans because of their lack of belief in Christianity. While Ehrman doesn’t make the comparison, it is easy to see some parallels between these aspects of early Christianity and extremist Muslim such as ISIS, using fear and violence to gain dominance for their religion. It is a salutary reminder that from early on, Christianity was not primarily a religion based on peace and love.

Overall, The Triumph of Christianity is an excellent survey of the literature and debates about the rise of Christianity, written in clear language, explaining ideas without using jargon, and without getting bogged down in too much detail. Even if it does not answer all the questions we might have about the role of religion in the Roman Empire, it does provide a broad view of the topic which can help readers pursue the issue elsewhere.

© 2018 Christian Perring

Christian Perring teaches in NYC.