Why are there so many strains of *Christianity? Consider the list of the larger **Christian groups represented in the United States - there are 22 denominations with membership of over 100,000 (when you list independent Baptist and non-denominational as denominations) considered Protestant, the Roman Catholic church and its splinter groups, the Eastern Orthodox Church and its splinter groups, the Mormons and their splinters, the Jehovah's Witnesses, the Quakers...it's mind boggling.
Of course, many people are a part of their respective faith group because that is all they have ever known. They were either born into it, or they were converted into it from a non-religious background. They have never given much thought to considering anything else.
However, for the many others (including myself) who have changed their Christian affiliation, why do they change?
There is a great book called "Journeys of Faith", co-written by four men who made the change from and to Evangelical Christianity, Roman Catholicism, Eastern Orthodoxy and ***Anglicanism. I've read books about conversions and de-conversions, listened to interviews by people who made those changes, and enjoyed online exchanges with others who have made similar decisions for themselves and their families.
Why do people choose one way or another? A recent Jocko Podcast involved questions from listeners, and one asked Jocko, "What is your workout routine, including jujitsu?" Jocko's response was that "everyone is looking for a formula", and that, aside from basic principles of nutrition, fitness, and discipline, there really isn't one. You figure out what you want, then you figure out what you need to do to get there, and then you have to follow through.
That flies in the face of what we think we do with matters of faith. We believe we dispassionately examine the arguments for and against a faith group or belief, than we choose the one that seems most logical to us. But, it not only isn't the case with fitness goals, it's the case with all of our choices. As Rev. Ashley Null summarized Archbishop Thomas Cranmer in the 1500's, "according to Cranmer's anthropology, what the heart loves, the will chooses, and the mind justifies. The mind doesn't direct the will. The mind is actually captive to what the will wants, and the will itself, in turn, is captive to what the heart wants." Jonathan Haidt, in his book “The Righteous Mind” explains the same thing - we are driven in a direction by our impulses, and guided carefully in that chosen direction by our intellect.
This is clearly the case with the story of conversions and de-conversions. Many de-conversions are about up-close and personal morality - the individual, or people close to them, are involved in behavior that is considered immoral by their current faith tribe. So, they find a faith tribe that justifies it (including no faith at all). It's never put quite that way, but you can see it in the narratives. "How could I say my sweet friend was condemned to hell" or "there must be a way to accept gays and still support marriage".
Conversions between faith groups with similar moral precepts, but different theological justifications for getting them, are less centered on moral desires and more about personality desires. The convert to Pentecostalism was "tired of dead worship". The Eastern Orthodox convert was "looking for something timeless". The Roman Catholic and the Presbyterian desire clear authority, but one is comfortable placing that authority in a group of people with seemingly impeccable historical cred, while the other looks to a Confessional statement that is unchanging. The Calvinists latch onto TULIP for certainty, and the Baptist doesn't want any authority but the Bible (according to their own personal understanding, of course). The KJV-Only fundamentalist, like the Presbyterian, also wants an unchanging authority, but theirs is more explicitly tied to a cultural conservatism than even a document. The ****Non-denominationalist likes the authority of self, where they can define their religion as "relationship" and not worry so much about creeds, confessions, culture, or history. The liberal Christian is looking for justification to promote the present culture they prefer (which is why liberal Christianity gets so few converts from secularism). Anglicans like a worship that is rooted in history, though they appreciate being able to choose what part of history that worship is tied to.
In one of my theology FB groups, a man told his story: he was a Baptist but eventually became a Presbyterian. He admitted that it wasn't really the overwhelming evidence of the Presbyterian position (on baptism particularly) that convinced him to make a change. What put him on the road to the change was the church he wanted his family to join. He went to the church because he knew there were doctrinal similarities to his Reformed Baptist preference, and he fell in love with the church, its people, its culture. It wasn't an overnight switch (it almost never is), but he admitted the most compelling part was not the logic, but the desire.
An RC friend recently said, "I desperately wanted RC to be wrong, but found out it wasn't." Perhaps she wanted it to be wrong, but what she really wanted happened to be exactly what RC was offering - a formula, a certainty; perhaps a historical foundation far beyond what she had experienced in her previous faith culture, combined with an authority structure that made sense to the western mind. The RC doctrine of papal & magisterial supremacy, allegedly unchanging over time, is very comforting in particular to those dissatisfied with experiences in Anabaptist-style churches (most Baptist, Pentecostal/charismatic, and non-denominational or independent churches). What the heart wants, the will chooses, and the mind justifies.
Christianity doesn't have a formula. Sure, it has the basics of the gospel message that Christ died for our sins according to the scriptures, rose on the third day, and ascended to heaven, one day to return. It requires assent to the Bible as the preserved word of God, and the creeds of the early church give shape to the basics of a Trinitarian faith which, in itself, is incomprehensible. But those are the unquestionable principles, with so much more of life and worship a little uncertain…to ambiguous. "By what authority", when pitched to the historic Christian faith, is "the Scriptures, authored by God, as generally understood by the church in all places, at all times, by all cultures". That is frustratingly insufficient for many. So, we latch onto Roman Catholic structure, or Presbyterian confessions, or the liberty of the authority of self. We don't like uncertainty. We are looking for a formula that satisfies what we want.
NT Wright is so frustrating to all of these groups, because he insists upon some obvious Biblical elements and is also vague about so many other, seemingly important, aspects of Christianity. What we may fail to consider is that each of those desires and structures have value, but none are essential elements of the faith that should lead to battles over who is the "true" church. Could it be that the uncertainty is meant to be a reminder of our frailty? Could it be that a God who is somehow three-in-one and became, somehow, fully God and fully man that first Christmas, has more than just himself that is left without clear explanation? Could it be, that the God whose thoughts are not our thoughts, and whose ways are not our ways, who justifies the ungodly, has reserved certainty in all things - even some important things - to himself?
* If you learn about the other major faiths, they are similarly fractured
** By self-designation
*** Other Anglican "conversion" books include "Evangelical is Not Enough" and "Evangelicals on the Canterbury Trail"
**** We all like the authority of self, but some like it more than others