The customer deserves to receive exactly what we have promised to produce - a clean room, a hot cup of coffee, a nonporous casing, a trip to the moon on goassamer wings.
Most things don't work like they are supposed to work.
Improving quality requires a culture change, not just a new diet.
In a true zero-defects approach, there are no unimportant items.
When in doubt, delete it.
You are going to be measured anyway by some means, fair or foul. Usually the one doing the measuring has nothing specific in mind; so he does it by the seat of his pants. Careers are destroyed in this manner.