Internal criticism: historical reliability
R. J. Shafer offers this checklist for evaluating eyewitness testimony:
1. Is the real meaning of the statement different from its literal meaning? Are words used in senses not employed today? Is the statement meant to be ironic (i.e., mean other than it says)?
2. How well could the author observe the thing he reports? Were his senses equal to the observation? Was his physical location suitable to sight, hearing, touch? Did he have the proper social ability to observe: did he understand the language, have other expertise required (e.g., law, military); was he not being intimidated by his wife or the secret police?
3. How did the author report?, and what was his ability to do so?
1. Regarding his ability to report, was he biased? Did he have proper time for reporting? Proper place for reporting? Adequate recording instruments?
2. When did he report in relation to his observation? Soon? Much later? Fifty years is much later as most eyewitnesses are dead and those who remain may have forgotten relevant material.
3. What was the author's intention in reporting? For whom did he report? Would that audience be likely to require or suggest distortion to the author?
4. Are there additional clues to intended veracity? Was he indifferent on the subject reported, thus probably not intending distortion? Did he make statements damaging to himself, thus probably not seeking to distort? Did he give incidental or casual information, almost certainly not intended to mislead?
4. Do his statements seem inherently improbable: e.g., contrary to human nature, or in conflict with what we know?
5. Remember that some types of information are easier to observe and report on than others.
6. Are there inner contradictions in the document?