Historian Niall Ferguson uses his latest Newsweek column to bat away arguments against an Israeli strike against Iran’s nuclear weapons capability. Among his more interesting responses is the counterargument to the notion that a “nuclear-armed Iran is nothing to worry about. States actually become more risk-averse once they acquire nuclear weapons.”

Wait. We’re supposed to believe that a revolutionary Shiite theocracy is overnight going to become a sober, calculating disciple of the realist school of diplomacy … because it has finally acquired weapons of mass destruction? Presumably this would be in the same way that, if German scientists had developed an atomic bomb as quickly as the Manhattan Project, the Second World War would have ended with a negotiated settlement brokered by the League of Nations.

The single biggest danger in the Middle East today is not the risk of a six-day Israeli war against Iran. It is the risk that Western wishful nonthinking allows the mullahs of Tehran to get their hands on nuclear weapons. Because I am in no doubt that they would take full advantage of such a lethal lever. We would have acquiesced in the creation of an empire of extortion.

War is an evil. But sometimes a preventive war can be a lesser evil than a policy of appeasement. The people who don’t yet know that are the ones still in denial about what a nuclear-armed Iran would end up costing us all.