Gygaxian naturalism

http://www.geekspeaker.com/on-gygaxian-naturalism/

  Maliszewski:

tendency, present in the OD&D rules and reaching its fullest flower in AD&D, to go beyond describing monsters purely as opponents/obstacles for the player characters by giving game mechanics that serve little purpose other than to ground those monsters in the campaign world.

Maliszewski waxes a bit poetic here.  While the term is enormously pretentious for pretend elfgames, the concept is integral to D&D.  Broadly speaking, Gygaxian naturalism is the mechanical expression of world simulationism.  Outside the sphere of D&D, I would describe it as “immersive mechanics,” or “rules expressing game reality through mechanical function.”  It’s the marriage of fluff and crunch, usually accompanied by lots of random tables..  By fleshing out the fantasy world through Gygaxian naturalism, D&D creates the illusion of a fantasy world–a world that might exist, at least within the imagination.