I've been reading and listening to podcasts about the Eastern Front in WW2 and I'm curious how Historians determine the validity of figures and claims made by Soviet and Nazi sources when there seems to be a natural desire by both sides to paint the other in the worst light possible.
Could you be more specific? Sources about what?
"[History] is the search for fact... not truth. If it's truth you're looking for, Dr. Tyree's philosophy class is right down the hall." - Dr. Jones
In all seriousness though, I think this is a valuable quote. I don't look for the truth of the past, I look for experiences of the past. For that propaganda is valuable - such-and-such is how some people experienced their lives. They made decisions from the information they had on hand, and they really couldn't do anything else. Whether we're talking about Soviets or Nazis or Romans under Augustus propaganda is an important measure of how people reacted to their lived experiences.
The important part is that the claims were made; not the validity of the claims.