I'm a Christian who got tired of trying to explain logical contradictions and fallacies, of believing things that made no sense, and of hearing, "It's a mystery" or "Some things are hard to understand" every time someone couldn't explain a passage of Scripture. One church teaches you can't lose your salvation and another teaches you can. Both teaching from the same book they claim is without error. I believe the book is without error, therefore, the Law of Noncontradiction says that at least one of those churches must be wrong. They could both be wrong, but at least one of them must be wrong. That started my journey. If I want to know what is true I need to see what was first. Whatever was first is true. You can't have false doctrine before the doctrine exists. Therefore what is first is true. If I want to know what is first I have to go back to the beginning ie. the early church. What an eye-opener that was. Much of what churches teach today would have been deemed heresy by the early church. I simply looked at their teachings, compared them to Scripture, and saw that the majority of what they said fit with Scripture. Since then I've studied different doctrines to see where they entered the faith. Because if the first Christians didn't know of them they had to come from somewhere other than the apostles. By doing that one can easily see where several doctrines that are considered Christian entered the faith. One can see where the doctrines of "Just War", "Penal Atonement", "Satisfaction Atonement", Trinity, "Pre-Trb Rapture", "Hypostatic Union" and others entered into the Christian Faith. The Faith of the early church was quite different than that of today. However, unless one studies church history they'll never know how far the church has strayed from its roots.
There's a saying, we don't know what we don't know. When one studies church history they'll learn the things that, today, they don't know