For the next 12 years, he [Bart Ehrman] studied at Moody [Bible Institute, a pillar of conservative Christianity], at Wheaton College (another Christian institution in Illinois) and finally at Princeton Theological Seminary. He found he had a gift for languages. His specialty was the ancient texts that tried to explain what actually happened to Jesus Christ, and how the world's largest religion grew into being after his execution.
What he found there began to frighten him.
The Bible simply wasn't error-free. The mistakes grew exponentially as he traced translations through the centuries. There are some 5,700 ancient Greek manuscripts that are the basis of the modern versions of the New Testament, and scholars have uncovered more than 200,000 differences in those texts.
"Put it this way: There are more variances among our manuscripts than there are words in the New Testament," Ehrman summarizes.
Most of these are inconsequential errors in grammar or metaphor. But others are profound. The last 12 verses of the Gospel of Mark appear to have been added to the text years later -- and these are the only verses in that book that show Christ reappearing after his death.
Another critical passage is in 1 John, which explicitly sets out the Holy Trinity (the Father, the Son and the Holy Spirit). It is a cornerstone of Christian theology, and this is the only place where it is spelled out in the entire Bible -- but it appears to have been added to the text centuries later, by an unknown scribe.