You know, this wasn’t a rule, but it sure was an entirely universal assumption among my gamer groups. Player knowledge is not character knowledge. That covered a lot of areas, but it really mattered in the case of good and evil characters, and how they ended up doing in the campaign.
You and I both know you are playing an evil character. We also know that I am playing a fairly dumb, but essentially neutral warrior. I don’t play that I know you are evil, but I don’t play that I have unreasonable trust in you, either. I don’t much care about this good and evil stuff, I want some loot, and some butt kicking. If you steal my loot, you butt will do just fine. We always played evil characters as evil, but not stupid. Over the long term, what happened was that the evils couldn’t effectively cooperate at anything but the lowest levels, or under the domination of one very powerful character. The killing of comrades was part of the evil. Not frequent, and usually not while out in the wilderness. But eventually, petty spats became blood feuds. I always felt it was realistic.
The good characters cooperated well, at all levels, and the neutrals eventually ended up being on their side because it was safer, and long term, more profitable. We did not play that all the people on the adventure today are long term associates, or friends. And the need to prove ones reliability was a part of the adventure. Rolling your eyes over the tendency of the Paladin to pray over the bodies of his conquered foes was common. The impetuous berserk fighter who ran off into the depths of the dungeon was a pain in the ass, but you ran after him, because he was your pal, or he was the cleric’s pal, anyway, and the Wizard thought highly of him, too.
Since the campaign lasted years of real time, game time ended up covering centuries. The good players were altruistic, and established permanent support systems for those willing to serve the cause of general weal. In the latter years, that ended up putting the good characters entering the game at level one very far ahead of the evil ones, in material things, such as equipment and supplies, and in logistical support.
Every part of the campaign was littered with orphanages, endowed with by the wealth of fabulous heroes of days gone by. We played a lot of orphans, later on. I played a boy who killed his parents in order to get into the Freeport Orphanage. One of my very few successful evil characters, John Foundling was a name that made player characters spit for years. But he had to adventure in new places and under assumed names, and he ended up running for his life, most of the time. My player friends hated him, but they did not hate me because of him. Or not much, anyway.
However, players always knew when the party was likely to include evils, under false colors. They could play it that way, without compromising the character’s information with their own. Perhaps I was far luckier than I knew, in that campaign.
Tris