Rules and What They're For

I've become quite a cynic in my time designing RPG systems.  For the most part I'm picky enough in my players that I don't get people whose express purpose in coming before my DM screen is to break games.  That I nevertheless feel like if I don't create airtight rules they'll be abused may be due to my own paranoia at all the people I don't deal with, or maybe it's due to the way in which the players who do come to my table (and myself, as well) discuss the ways we could be breaking systems but don't that, when I finally started making my own games, I was extraordinarily careful to observe corner cases and the way in which things are abused.

I see a lot of games with cool ideas but deeply flawed rule sets, the kind of games that are very easily taken advantage of and 'broken,' creating unbalanced characters or situations.  Often character options are not balanced against each other very well, if they can be said to be balanced against each other at all.

The stance these game seems to take is "Rules exist to create a consistent and fun experience for all participants." And I can get behind what they're trying to say, but I can't help but think that it's very short-sighted.  My personal thesis for the purpose of Rules (in any context) is the following:

"Rules exist to encourage behavior."

And the part that's really easy to overlook is that they will encourage behavior whether you want them to or not.

I'm going to use a video game analogy because it'll prevent me from pointing fingers.  In World of Warcraft, how do the designers know what the best damage-dealing build is?  It's not by looking at the numbers they created: it's by looking at what their players use to kill their toughest bosses the fastest.  What is popular is what functions best at accomplishing the goal, what is poor at it is underused.  The designers are unintentionally encouraging players to use the powerful builds, but they are encouraging it.  Tabletop games are not MMOs, but so long as players want to be effective at accomplishing their goals, they will follow the same model: they use the rules to be as good at it as they possibly can.

This is also visible in disadvantages, especially in point-buy systems.  Such games encourage players to downplay the weakness and attempt to avoid any statistical failing if not just outright ignoring the weakness' very existence, after all, the player was rewarded for putting it on his sheet (that's what he got the points for), not for keeping it there or making it a part of the character.

This is the single best way to integrate your system and your setting: create a system in which the most effective way for your players to achieve their goals is one that fits with the world you've created.  This applies in GMing too: if your players learn that when they leave their defeated enemies alive that their enemies will consistently stab them in the back or escape, you're encouraging your players to kill the enemies they defeat, and that will affect the flavor of the game you're running.

This thesis is a cornerstone of my gaming theory, and I'll call back to it often: "What behavior does this encourage?  Is that the behavior you want to encourage?"