In order to determine whether a particular thing is "reliable," it is important to know the purpose for which the thing is going to be used.
If my wife asks me how big the living room is because she is going out to buy paint, I might just pace off the length and width and do a calculation in my head. If she gives that measurement to the clerk at the paint store, she will probably come home with a reasonable amount of paint. However, if my wife were planning to buy wallpaper, I would not consider this a reliable measurement. I would want to measure and calculate precisely, taking into account the location of doors and windows so she could get the right number of rolls. A measurement that is reliable for one purpose might not be reliable for another. When it comes to the reliability of the transmission of information, the same point holds. A method I might consider reliable for transmitting the results of a football game would likely be completely unreliable as a method for transmitting orders to a submarine to launch nuclear missiles. The latter demands much greater accuracy and security.
That is why I find comparing the reliability of the Bible to the reliability of other ancient writings meaningless. No one wants to use the Iliad for the kind of purposes for which conservative Christians want to use the Bible. No one shows up at school board meetings demanding that the curriculum be controlled by what the Iliad says about homosexuality or the origin of species rather than what the scientists at leading research universities say. Nobody tries to find exact and certain answers to complex questions in the Iliad in the way that conservative Christians try to find them in the Bible. The only meaningful comparison would be to another historical record that claims the same kind of exactitude and certainty.
Unfortunately for the Christians' case, historians never seem to claim the kind of certainty and exactitude for any historical record that conservative Christians claim for the Bible. For example, if a historian wanted to study the Battle of Gettysburg, he could look at contemporaneous reports, letters, and diaries written by soldiers of every rank from both armies as well as memoirs written in the months and years afterwards by eyewitnesses to the events. He could read first hand reports in articles from newspapers and periodicals of every political persuasion. He could walk the battlefield and examine artifacts. Nevertheless, the historian would never claim absolute certainty about every fact or detail of the battle.
Despite the wealth of contemporaneous source material with which to study an event that took place one hundred and fifty-four years ago, there are many aspects of the Battle of Gettyburg, both large and small, about which historians are unsure. They are not sure how many men participated in Pickett’s Charge. They are not sure how Union General Custer and Confederate General Stuart came to fight a cavalry battle behind the Union lines on the third day. They are not sure whether Confederate Commander Lee complained about General Longstreet’s slowness. Moreover, even the things they are confident about are subject to revision by new evidence and explanations. Bible believers, on the other hand, claim to have absolute historical certainty about events that occurred two thousands years ago based on anonymous accounts written thirty to sixty years after the events in question.
Christians claim that the Bible compares favorably with other ancient historical documents, but they make claims that are totally unlike any claim historians would make about any document ancient or modern. No historian believes he has the exact words given in speeches in the Roman Senate, but Christians believe that they can know exactly what Jesus said. No historian believes he has every relevant bit of information about Caesar, but Christians believe that the New Testament contains everything they need to know about what Jesus said or did. They believe that nothing he said or did outside of that which is recorded in the Gospels could affect their understanding of his purposes. Every historian knows key details can be altered or invented for political purposes, but Christians believe that nothing that Jesus said or did was distorted between the time he died and the time the gospels were written thirty to sixty years later. Every historian knows that there is frequently more than one possible explanation for the data and that any given explanation can only be considered the most likely or best supported, but Christians believe that their understanding of how the New Testament came to be written can be adopted to the exculsion and categorical rejection of all others.
So when I hear a Christian assert that the Bible is better attested than some other work of ancient history, I am unimpressed. Given the way the conservative Christian relies on the Bible, it would have to be better attested many times over than every work of history ever generated up to and including this morning’s newspaper.