The excellent thing I learned about 5 whys is that not only is it not really just 5, as you allude to with “5+”, but it’s also a *tree* instead of a linear list

The excellent thing I learned about 5 whys is that not only is it not really just 5, as you allude to with “5+”, but it’s also a *tree* instead of a linear list. Often a why will lead to more than one answer, and you really have to follow all branches to completion. The leaf nodes are where the changes are necessary. Rather than identifying one single thing that could have prevented the incident, you often identify many things that make the system more robust, any one of which would have prevented the incident in question.