Age of Decadence - What is an RPG?

Vince from Iron Tower has penned a piece titled What's a roleplaying game? at The Age of Decadence forums.  It's a well-trod subject but as Vince says, at least you'll get an understanding of the philosophy behind AoD:

Obviously, role-playing games are about playing a role or two, but what does it really mean? Every game puts in a role of something or someone. Doom puts you in a role of a brave, ass-kicking, silent but deadly space marine who really doesn't take no for an answer. Windows' Minesweeper offers you to play a role of a brave ninja cartographer who uses nothing but his wit and logic to map an unforgiving minefield. So, "playing a role" definition can't help us here as it's big enough to put every game under its roof.

Playing a role in the CRPG context means making decisions fitting your character. Let's say you're playing a thief and you're facing a well guarded gate. A warrior may decide to fight his way through here, but a thief may decide to find another way in. That's the core difference between RPG and adventure games, for example. In adventure games you make no decisions but progress from point A to point B to point C in a very specific, set in stone way. The Monkey Island brilliant series, The Dig, Full Throttle, etc – each playthrough is exactly the same.