What's the most undervalued, under-discussed commodity on the leadership stock exchange today? What's the item that is currently on no one's list of desired qualities in a leader that once would have been consistently in the top four?

It's not courage or willingness to risk. Every motivational speaker trumpets those.

It's not humility or strength of will—Jim Collins has placed these squarely on the path from good to great.

It's not the ability to identify strengths—Marcus Buckingham and others have built a movement around strengths.

It's not creativity (think of Steve Jobs), or unleashing core competencies (think Gary Hamel), or the capacity to persist in the face of crushing failure (think Winston Churchill or the Chicago Cubs or pretty much anybody on Dancing with the Stars).

So what is today's most undervalued leadership trait? It's prudence.

Allen Guelzo has written a wonderful book on Abraham Lincoln, and he devotes an entire chapter to the role prudence played in the life of ...