For one thing, the early church fathers said that Matthew, Mark, and Luke were written by the biblical characters we're familiar with. Blomberg wonders why the early believers would have attributed these writings to such unlikely candidates as Matthew, Mark and Luke if they were written by others. Mark and Luke weren't apostles. And Matthew didn't have an especially good reputation. Another argument Blomberg presents is built upon the date of the book of Acts.
Acts ends abruptly with no record of what happened to Paul.
Since Luke drew from Mark, Mark must have been written earlier still. A case can be made, then, that the Synoptic Gospels were written within about 30 years of Jesus death. This puts them close enough to the events that the facts they report could be corrected if wrong. The Gospel Writers and Historical Truth Assuming that we have presented a plausible argument for early dates for the Synoptics, this still leaves unanswered the question whether the writers intended to write factual history. On the program, Prof. Dominic Crosson suggested that we are mistaken in taking the Gospels factually because the writers didn't intend us to do so.