WayneLigon
Adventurer
You've answered your own question right there, really; the revelation of the true nature of reality - instead of the small tiny portion we're normally equipped to understand - is what causes the madness. The exact nature of that reality is, of course, unknowable. If you did know it all, and understood it all, you'd be nutsNisarg said:Now, add to this the fact that a PC can lose sanity, and end up going totally nuts, just by reading "Mythos Books" filled with things man was not meant to know.
That would imply that it is the mere knowledge of the truth of reality that is the cause of this insanity.
The 'meaning of life' viewpoint has some validity. Almost everyone who isn't already crazy beleives there is some point to life, that it has some meaning even if that meaning is contained only within philosophical constructs we make ourselves or have presented to us (both atheist and the religiously-inclined do this; the religeously-inclined can say 'It's X's Will' or 'This, too, serves X's purpose in some way'; the atheist creates meaning from her actions or how she affects the world around her). The idea of revealing that there is no point to existance and never has been will - should - eventually gnaw at the sanity of the affected person. Repeatedly having it thrown in your face eventually drives them mad.
The biological viewpoint has validity as well. Humans are only equipped (within the context of Mythos fiction) to perceive certain dimensions or colors. Being forced to endure exposure to Otherness is what leads to madness as the mind tries to perform the required operations to perceive this new reality and fails.
Seeing deaths and blood and gruesomeness don't normally produce insanity in stable personalities but pretty much everyone is going to have a bad reaction facing such a thing. Seeing it time and again can indeed unhinge an unstable personality (most of the people in Mythos fiction fall into this catagory - virtually all of them also come from a time when they were not exposed to movies and TV. The modern day CoC rules mention this effect, I think, and give some guidelines about it), especially if it's not their job to see such things.
People like cops and firemen and coroners eventually 'get used to it' (a very inadequate term but it's not the place to go into the mental 'compartmentalization' that some people in those lines of work go through), though even some of them eventually have to leave the profession. The people who don't seem to bat an eye at the most horrendous acts of carnage can either be what some psychologists refer to as 'invulnerables' (read:, we don't know why these people don't freak out when everyone else does) or they are in fact suffering from one of the milder forms of insanity where they block emotions.
In game terms they'd be 'temporarily insane' with repeated exposures that keep sending them back across that line; insanity doesn't mean you can't function. In fact when you go to 0 SAN, you kind of 'come back around from the other side' and can function with normal people again.
All in all, though, searching for a 'real world' reason is just useless. It works like that because the stories the game is based on work like that and the SANity rules are there to make sure it continues to function like that and people can't say 'Hey, that guy just fell into a 400-degree angle and vanished. See it, eh'.