A "why-by" ladder is sometimes useful when you're trying to work with a group to:
get them to consider a higher-level objective, or conversely
get them to be more specific or concrete
In the diagram below, each downward arrow is where you would ask "by?" or "how?" in order to reach a lower "rung" on the ladder.
Conversely, if you're looking to reach a higher level objective, you'd ask "why?" instead.
I honestly can't remember to whom this should be attributed but I think I encountered it via the Account Planning Group.