Richard Bulliet is professor of history at Columbia University and author of Islam: “The View from the Edge” and “The Case for Islamo-Christian Civilization.”

Osama bin Laden, the visual icon of terrorism in our fear-driven age, is gone. No one can replace him.

Jihadists will doubtless commit new outrages and hatch new conspiracies. But warriors committed to sacrificing their lives for his murderous cause are a wasting resource unless they can draw new recruits into their ranks. And while Bin Laden may or may not have been the mastermind behind the attacks launched by Al Qaeda and its imitators, he was unquestionably their master recruiter.

Any number of studies have analyzed the intricate pathways by which a young computer programmer here, an out-of-work immigrant there, or the raped widow of a suicide bomber somewhere else have found their way into jihadist cells in a score of countries. Mosque-based activists nurture some, family networks ensnare others, and a few develop overwhelming feelings of outrage or victimization just by reading the news or watching videotapes.

But Osama bin Laden spoke to everyone, including many millions of Muslims who admired his analysis of world affairs but never themselves developed the courage and commitment to follow his logic to its lethal end. He inspired both the suicide bomber and the armchair critic of American and Israeli imperialism....