True witnessing — and bearing witness — can’t happen at some secure remove from reality. They require the presence of the observer at the event, Goya’s “Yo lo vi (I saw this)” from “The Disasters of War” to give their testimony force. Tim Hetherington’s passing reminds us of the price all too often paid by others for our ability to engage vicariously with the cruelest events of our times, and of our obligation to honor those who thus serve in our stead. […]