Democracy thrives on civil debate, Michael Sandel says but we're shamefully out of practice. He leads a fun refresher, with TEDsters sparring over a recent Supreme Court case whose outcome reveals the critical ingredient in justice.

Four bridges and innumerable tunnels and drainage canals connect Ciudad Juárez and El Paso, Texas. Rival cartels sparring for control of a plaza, the name given to any trafficking route, butcher each other and the security forces.