Why Do Christians Try to Convert People? I begin this New Year by addressing a really interesting question I received recently from a reader. It’s a question that has rarely occurred to most people. Today, we tend to think that religions are by their very nature interested in converting others to their views, that they are just inherently evangelistic, missionary, and proselytizing. If your religion is “the right one,” wouldn’t you want everyone to agree with you, so they too could be right, instead of wrong? Wouldn’t their salvation depend on it?
That indeed has long been the view of both Christianity and (later) Islam and … well surely all religions, right? Uh, as it turns out, the answer is No. In the world that Christianity came into, for example, in the Roman empire, there simply weren’t such things as missionary/evangelistic religions. Huh? Then why was Christianity?
Here’s the question I received.
Why Do Christians Try to Convert People?
Where/how/why did the new religion ‘about Jesus’ becomes – unlike most contemporary religions up to that point – a proselytizing one? That is, why did Paul and, presumably, others care whether others converted? Obviously, Jesus reportedly commanded them to do so, but do you think those ‘commissions’ really go back to Jesus?
This is one of the key questions I addressed in my book Triumph of Christianity. I did so only after explaining that all the Roman religions were polytheistic (‘pagan” more or less means polytheistic), with many gods, all of whom deserved to be worshiped, and none of whom insisted that they alone should be worshiped. So it was acceptable and everywhere practiced that people would worship all the gods they wanted, and none of the gods insisted that you worship them alone. So there was no incentive to try to win “converts.” Christianity was different. It had the only true God and it was missionary about it.
Here is what I said about the matter in my book. This will take two posts.
Christianity as a Missionary Religion
Even if pagans who adhered to one cult or another may have liked others to join them in their rituals of worship and welcomed them when they chose to do so, we have no evidence of organized efforts to make it happen.
As a prominent historian of Roman religion, Ramsay MacMullen (author of Christianizing the Roman Empire), states: “Of any organized or conscious evangelizing in paganism there are very few signs indeed.”  In fact, we don’t know of any missionary religions in the pagan world.
Not even the mystery religions appear to have employed organized efforts to bring in devotees. It is sometimes said that the expansion of Mithraism presupposes some kind of mission, but that turns out not to be true. The religion spread essentially by word of mouth from friend to friend, family member to family member – at least among adult males.
Why Do Christians Try to Convert People? The Concept of Evangelism
None of that is particularly surprising. What may be far less expected is that ancient Judaism also lacked any genuine missionary impulse. This claim cuts against what scholars had long argued, that the Christian concept of an evangelistic religion had been inherited from the Jews. But more recent scholarship has persuasively shown that this was not the case at all.
Of course, Jews typically did welcome anyone who seriously wanted to consider adopting their worship and ways. We do have records of pagans converting to become Jews. Among other things, this meant that converts, if men, were circumcised and, if men or women, went through the process of being admitted into the Jewish fold and agreeing to observe established practices of worship and custom.
There were other pagans who might be thought of as “Jewish sympathizers.” These would be gentiles who chose, for rather obvious reasons, not to be circumcised and possibly not to follow the entire set of prescriptions in Jewish law. But they would have worshiped the God of the Jews and possibly him only, in synagogues with Jews, and participated in Jewish life as members of the community with a kind of secondary status. Sometimes these people are called “God-fearers” because they revered the one God even if they chose not to adopt certain Jewish identity markers.