Should you trust it?
We’ve talked about primary sources, now about vetting the information. We will get information from several sources during our research, we need to rank that qualitatively somehow. For example, if we want to know physically the building where John Doe lived in 1944. A search found the address 101 Main Street, Tinytown, Texas.
If we use google maps, it gives us a location on a map of A-B-C. Yet, MapQuest gives us D-E-F and the Census maps show D-E-F. However, an old photo shows no buildings there but a building 100 yards south is a likely candidate.
While on site getting ground truth, you wrangle in an old timer who says, “John? Ya he lived in the red brick building over yonder where that chimney now lies on its side” which happens to be about where the building was in the photo. Hopefully your instincts are telling you more authority should be given the old timer’s location than Google or MapQuest, but why? Common sense is trying to tell you to trust the primary source, your brain is also processing the fact that current geo-coded addresses will not line up with 60 year old postal addresses.
A soldier writing in his diary the day after a battle to tell the tale of what happened will have the bias of his side of the story. It will also be a fresh rendition of the even. The soldier writing a letter home to his wife a week later will have another bias, likely so he doesn’t scare his wife. That soldier writing a memoir for publication about the battle 3 years later will have a greater bias, as he needs to cater to a larger market to sell his book.