The heart of any RPG is its ability/attribute score system. This reflects the ways in which the characters interact within the fictional world. In effect, it is the physics of the world as experienced by an individual. Thus, the refinement of the mechanics must always be based on the categories that represent the basic capacities. In these styles of games, this is, at minimum, a score for physical aptitude and one for mental faculties.
A two-stat system is simple and possibly quite malleable, but probably not deep enough to simulate anything but film. This is not to say that cinematic action isn’t enjoyable, only that it is limited in scope and the value of diminishing returns. To prevent this requires a third stat to measure the character’s strength of will or spirit. This creates the illusion of the so-called three-dimensional character so highly prized in the literary arts. Or, for the modern reader of novels, the minimum elements for believability in the “reality” of a character’s ability to leap off the page. Games of this type are more robust, but run the risk of straining options and limitations placed upon the game as inherent in a genre.
To combat these issues and provide a multiplicity of genres and accommodations for play styles, a greater number of attributes are needed, which both increases the game’s complexity and the number of dimensions of interaction between the character and the world. The single limiting factor that prevents the system from collapsing under its own weight is the reliance of a core mechanic that not only serves as the glue and underpinnings of the game, but doubles as the simplifying device that prevents potential players from abandoning the game before having given the game a chance to reveal its possibilities.
Any system employing multiple categories for attributes must maintain as close as possible an equal number of physical and mental stats. The reason for this is to preserve a balance of actions between the two prominent plot types common to dramatic forms: plots of the mind and plots of the body. Why is this the case? Because one of the primary sources for these games is literature, to include the works of playwrights. The format of the game is rooted in oral storytelling techniques, but everything else defaults to the technology of writing.
Like film, the RPG must borrow from the novel to create characters that serve as more than images if a story is privileged above the act of moving pictures. Stage techniques are mainly useful for the gamemaster to create the game world, thus it doesn’t readily aid in seeing how multiple attributes expand the game’s interfaces. That is if one is unwilling or unable to discern how an actor’s performance is infused with a different skill set that dictates the strengths and dimensions of the character portrayed when compared to another actor. This isn’t just a different set of stats in an RPG, but rather potentially an entirely new set of attributes. Reaching? Maybe, but inspiration for how many points of entry/interface between players and the world of their characters nonetheless.
These are the considerations one must make when defining what the game can handle while setting the complexity level of the simulation. The dividing line between nuance and simplicity of storytelling and character design, not game mechanics, lies in the number and type of attributes. The core mechanic remains untouched, it is the design of character creation that colors the view of the system’s complexity. The fewer the number of rules governing how to generate a character, the easier the entry into the hobby, but it comes at the cost of exactness in how and when the rules are applied. In the parlance of the literary community: do you prefer plot or character? For the gamer: few stats or many? This determines the core audience of the game.