Years from now, when many of us spend a large chunk of our lives in virtual worlds like Second Life, someone will write a history of the idea of the metaverse, the unreal 3-D spaces in which people interact with avatars. The game World of Warcraft will loom large in that book, as will Snow Crash, the 1992 novel in which Neal Stephenson coined the term "metaverse." Going back further, so will MUDs, the "multi-user dungeons" first developed on university computer systems in the late seventies.

MUDs drew their name and inspiration from Dungeons & Dragons, a fantasy role-playing game designed by Gary Gygax, who died last week at 69. You may not have heard this, since Gygax wasn't exactly a household name. But he helped invent the world we'll live in.

That seems like an extraordinary claim for a geeky-looking game designer who developed a hobby enjoyed by thousands of teenage boys — and at least a couple of girls. Most of those who remember the game fondly, including me, are vaguely embarrassed that they wiled away sunny afternoons in suburban basements throwing three, ten, twelve, and twenty-sided dice to determine the course of a game that lacked a board, a winner and a definite ending. One person would serve as the dungeon master, telling the other players what situations they faced. The players would decide on a course of action, then roll various dice to determine how they fared. The action — swordfighting, spellcasting, and such — took place entirely in everyone's imagination.

In other words, the game took place in a virtual world. That world was represented only on graph paper and in teenage imaginations. But any of the 10 million people who play World of Warcraft would recognize Dungeons & Dragons as an experience very similar to the one they enjoy today. Players fight monsters, search for treasure and try to remember to go outside every so often.

Virtual worlds are moving into the mainstream, and MTV is working on one based on the Lower East Side of Manhattan. I'm guessing that it will look less like World of Warcraft than "World of MySpace," but that's exactly what makes Gygax so important. He changed the world we live in by helping to pioneer the notion of a virtual one. When the history of unreal worlds is written, Gygax will be among the most important figures.