Jef Raskin's The Humane Interface

Tasks become habits. No modes, only chording. Only one way to do things. No warning screens, everything is undoable.

Reliable. Everything saves automatically. Content resistant to crashes.

Efficient and simple. Tasks don't take time to perform. Tasks don't take time to learn.

No icons. Purely text.

Zooming UI. No filenames.

No applications. Only commands.

Well tested.

Visually attractive.

>>7
People develop habits. Habits are good because then you can focus on other tasks. Thus, asking for confirmation is bad because users will develop a habit of confirming the command, or the interface will be obnoxious to use. Thus, commands must be undoable. Furthermore, adaptive user interfaces are bad, if the adaptation interferes with habits formed.

If there is only one way of doing things, then people develop habits and feel secure and in control. If there are too many choices, it is difficult to teach, and difficult to use because you have to decide how you will do something.