This is a challenge I found worth taking. I am working it out. The basics for it I am pleased to say were present in me all along. However, as any writer knows, it's how you say it that is more than half the battle. Saying it well means you have refined it well in your mind as did Dr. Martin Luther King, Jr. What follows is a very rough draft with the basic "Why" statement followed by its explanation in multiple parts. Is this the sort of vision you'd follow? Does this inspire action in you? I'd like to know.
To hear the original TED talk, go to: http://www.ted.com/talks/simon_sinek_how_great_leaders_inspire_action.html
I encourage you to take the challenge yourself. It is quite the exercise.