Here’s an old riddle I heard at a party recently:
“A family of four needs to cross a bridge. Only one or two can cross at a time. They must share one flashlight which must be brought back after each trip. Father takes 10 minutes. Mother takes 5 minutes. Sister takes 2 minutes. Brother takes 1 minute. They must get across in 17 minutes total. What order should they go in?”
It sounds impossible – the intuitive “best solution” takes 19 minutes (Brother escorts each of them across and then returns for the others, 10+1+5+1+2 = 19).
I spent 30 minutes trying to discover “out of the box” solutions. Dad carries Sister? They find a boat? Toss the flashlight back across the bridge? I was assured no such tricks were necessary. Finally I set out to prove the problem impossible, as follows: Five trips are necessary. A trip with Dad takes 10 and a trip with Mom takes 5, for a total of 15, leaving only 2 minutes remaining to make three trips. Impossible, right? Yes, if Dad and Mom go separately. So if there is a possible solution, it must involve…
That line of thinking led me to the simple “in the box” solution (which you are welcome to email me for if you can’t figure it out). And I realized there is a lesson here. It has become fashionable to think “outside the box,” as if that is a virtue and and the best answers are always “out there.” Maybe sometimes they are. But other times the best answer is right here inside of the box, over in a corner you neglected to check out.
This is a lesson for engineering design, where the search for clever solutions can cause us to overlook some mundane but highly effective solutions. Life is that way too, sometimes. We want a clever diet rather than a simple admonition to “eat less and exercise more.” We want a prescription for Christian growth more exotic than “read your Bible, pray every day.” Maybe, just maybe, the solution is inside the box after all.