A fter every major disaster, especially of the man-made variety, there is a public outcry that demands: Do something! The cry is rooted in a well-founded frustration with our inability to attain perfection in an imperfect world.

If we can harness the atom/invent the microwave oven/put a man on the moon, why can’t we make a cruise ship that won’t fail/invent batteries that won’t cause fires on airplanes/prevent massacres by deranged gunmen? It is the latter, of course, that causes the strongest demand for solutions, doubly so when the victims are children on a school campus.