The four XP values

Quite by chance I've notice several recent blog entry quotes mention the four XP values:

• Communication: Community has to do with communication.
• Simplicity: The art of maximizing the amount of work not done.
• Feedback: Practicing without feedback is like bowling through a curtain that hangs down to knee level.
• Courage: One thing that never ceases to amaze me is how relatively few people understand what courage is. The absence of fear is not courage; the absence of fear is some kind of brain damage. Courage is the capacity to go ahead in spite of fear.