Lesson 2. How Historians Weigh Evidence

Historians do not have laboratories. They cannot repeat the past, so they reason from what it left behind: documents, objects, inscriptions, and the testimony of people who were there. Faced with a claim about the past, a historian asks a short list of questions.

• How early is the source? Closer to the event usually means fewer links in the chain.
• How many independent sources are there? Independence matters more than number.
• Did the writer have a reason to lie? And does the account contain material that works against that reason?
• Does it fit what else we know? Places, officials, customs, dates.
• Is there hostile corroboration? An opponent conceding a fact is worth more than a friend asserting it.

These are the ordinary tools of ancient history, applied to Homer and Tacitus as much as to the Gospels. Nothing in this course asks for a special rule to be made for Christian sources.

Suppose five newspapers report the same story. If four of them copied the fifth, you do not have five witnesses; you have one witness and four repetitions. This is the single most common error in popular argument, and it appears on both sides.

It matters directly here. Matthew, Mark and Luke share so much material, sometimes word for word, that literary dependence between them is the standard scholarly explanation. An argument that counts the Gospels as four fully independent witnesses will be corrected by the first informed person who hears it. Conceding the point up front costs nothing and keeps everything else you say standing.

The reverse error is just as bad. Dependence between documents does not make them worthless: a source that another writer trusted enough to use is itself evidence, and the places where the accounts diverge are where independent information may show.

Someone will object that the Gospel writers were believers, so of course they wrote favourably. The observation is correct. The question is what follows from it.

If testimony only counted when the witness was indifferent, we would have to discard most of what we know about the ancient world, because people generally write at length about what they care about. A historian's response to an interested witness is not dismissal but cross-examination:

• Does the account keep material that is awkward for the writer's own case?
• Does it name checkable people, places, offices and customs?
• Where it differs from a source it used, do the differences look like independent memory or like tidying?

Historians call the first of these the criterion of embarrassment. All four Gospel accounts name women as the first to find the tomb empty, in a setting where women's testimony carried little formal weight. A group inventing a persuasive story for that audience does not open with witnesses that audience could discount.

1. A friend says: five websites report the same claim, so it must be true. What question should you ask first?

2. Explain in two sentences why a hostile source conceding a fact carries extra weight.

3. Give one example of a detail in the Gospel accounts that the writers would plausibly have preferred to leave out, and say why keeping it is evidentially interesting.

4. Narration. List the historian's five questions from this lesson in order.

1. Are they independent, or are four of them repeating the fifth?

2. A hostile writer has no motive to strengthen the other side's case. A concession against interest is therefore hard to explain except by its being true.

3. Women as the first witnesses at the tomb is the standard example; the disciples' repeated failure to understand, and Peter's denial, also qualify. Keeping such material is difficult to explain if the account was shaped purely to persuade.

4. How early; how independent; motive to lie; fit with what else is known; hostile corroboration.