There are some very interesting "revelations" about the nature of ‪RPG‬ in the Official Book of ‪‎Ultima‬. This one is really important

"With Ultima IV, Garriot resolved to forge a world in which he could demonstrate the logical nature of ethical values... and why it makes sense for people to live by such values as natural habits in the game world, not just because the quest says so, but because the world will react more favourably to you. The antithesis of that as a habit is that the world will react negatively against you.
...
That is the whole story of Ultima IV. The quest you have to fulfill is largely irrelevant. The fact that you have to take item A to location B to solve the game is not what it's about. The game is about social issues of being a good person the world as opposed to evil person"

This is exactly the principle that I have personally kept as a guideline while designing RPG worlds. World should be like a real world which reacts to anything you do in a "logical" manner. Meaning that always there should be a clear reason to everything that happen. However, these reasons do not have to be clear to the player. That is part of the puzzle to find out why things happen as they happen. IMO Ultima parts IV - VI succeeded in this.