When the plumber knocks at your door, why do you let him in? He's probably bigger and stronger than you. And he has a wrench. He could easily kill you and steal your money and your stuff, which would certainly be a better deal for him than receiving a moderate payment and having to fix your toilet.

But you trust that he won't; and trust, that mysterious and invaluable substance, is the subject of Bruce Schneier's ambitious "Liars and Outliers: Enabling the Trust That Society Needs...