Before I do anything else, I want to say how much I'm enjoying this topic! It's really given me some excellent sources and ideas on things, and for that I wanted to say thank you.
But then, I read this, and it got me to thinking:
The Atom, which I ventured (to the disgust of my scientific friends) to make fun of 30 years ago, has now exploded of itself as thoroughly as a German "coal-box"; and the fixed Chemical Elements of older days have of late dissolved into protean vapours and emanations, ions and electrons, impossible to follow through their endless transformations. As to the numerous "Laws of Nature" which in the nineteenth century we were just about to establish for all eternity, it is only with the greatest difficulty that any of these can now be discovered—most of them having got secreted away into the darkness of ancient text-books: where they lead forlorn and sightless existences, like the fish in the caves of Kentucky.
Civilisation: Its Cause and Cure by Edward Carpenter
You know, this raises a very interesting point. Considering how rapidly things have changed in the world since the 1920s (or worse, the 1890's) it's very difficult for a thoroughly modern player to recapture some of the attitudes of yesteryear. While that's a good thing when it comes to things like racism and colonialism, it does make it very difficult for players to actually play someone from even those relatively recent times. Take attitudes towards sex and marriage alone, and you'll see what I mean. Thinking about things we KNEW were true as could be in the 1970's and now are completely discredited a mere 40 years later sort of brings the issue home. And if you think about the attitude towards science in the 1890's through just prior to World War I ("it is an unmixed blessing and will solve everything for everyone") and the post Great War attitude that started making scientists more amoral or even evil (to say nothing of how the attitude towards science and scientists in general changed even more for the worse in the 1950's and 60's in the wake of the atom bomb), and you begin to understand just how hard it is for a player to immerse himself in the proper mindset. What they saw as "normal" we see as either ignorant, or, at best, naive.
Now compound the problem by trying to think like someone in the Dark Ages or Imperial Rome. As a historian, I've actually spent some time thinking about this issue, and was forced to reach the conclusion that a medieval monk or a Roman Centurion thrust into the 20th century would undoubtedly either go almost immediately insane or would be convinced he'd died and gone straight to hell or whatever the Roman thought was the equivalent. Conversely, any modern person sent back in time, even as recently as the 1600's, would almost certainly be burned as a witch.
In short, one of the biggest problems or issues we confront as Keepers is how to establish atmosphere meaningfully when you can't actually do things the way they were really done in the 1920's. Women, for example, are a major component of modern roleplaying, but if they were treated in classic era CoC as they really were in the 1920's, the Keeper would probably be found with his throat slit from ear to ear one day. And who would blame her?
So while this is pretty off-topic (and for that, I apologize to Paul and all of you following this thread), it does seriously give one food for thought.