Root-Cause Analysis

I like these concepts:

• If something can go wrong, it will. (Murphy's Law)
• People are, well, people. Everybody makes mistakes.
• Everybody is doing the best job they can given their abilities and knowledge.
• When mistakes occur, blame your process, not people.

and the approach:

• Ask "why" five times

(from The Art of Agile Development: Root-Cause Analysis)