Ehrman has explained his journey to agnosticism many times. Here we go:
âFor most of my life I was a devout Christian, believing in God, trusting in Christ for salvation, knowing that God was actively involved in this world. During my young adulthood, I was an evangelical, with a firm belief in the Bible as the inspired and inerrant word of God. During those years I had fairly simple but commonly held views about how there can be so much pain and misery in the world. God had given us free will (we werenât programmed like robots), but since we were free to do good we were also free to do evil. [âŚ]
In my mid 20s, I left the evangelical fold, but I remained a Christian for some twenty yearsâa God-believing, sin-confessing, church-going Christian, who no longer held to the inerrancy of Scripture but who did believe that the Bible contained Godâs word, trustworthy as the source for theological reflection. And the more I studied the Christian tradition, first as a graduate student in seminary and then as a young scholar teaching biblical studies at universities, the more sophisticated I became in my theological views and in my understanding of the world and our place in it.
Suffering increasingly became a problem for me and my faith. [âŚ]
Eventually, while still a Christian thinker, I came to believe that God himself is deeply concerned with suffering and intimately involved with it. The Christian message, for me, at the time, was that Jesus Christ is the revelation of God to us humans, and that in Jesus we can see how God deals with the world and relates to it. He relates to it, I thought, not by conquering it but by suffering for it. [âŚ] What is God like? He is a God who suffers. The way he deals with suffering is by suffering both for us and alongside us.
This was my view for many years, and I still consider it a powerful theological view. It would be a view that I would still hold on to, if I were still a Christian. But Iâm not.
About nine or ten years ago I came to realize that I simply no longer believed the Christian message. A large part of my movement away from the faith was driven by my concern for suffering. I simply no longer could hold to the viewâwhich I took to be essential to Christian faithâthat God was active in the world, that he answered prayer, that he intervened on behalf of his faithful [âŚ]â
http://www.beliefnet.com/columnists/blogalogue/2008/04/why-suffering-is-gods-problem.html