At a moment of serious challenge, battered by two wars, ballooning debt, and a faltering economy, the United States appears to have lost its capacity to think clearly. Consider what passes for national discussion on the matter of Iran. The open question is whether the United States should or will attack Iran if it continues to reject American demands to give up uranium enrichment. Ignore for the moment whether the United States has any legal or moral justification for attacking Iran. Set aside the question whether Iran, as Secretary of Defense Robert Gates recently claimed in a speech at West Point, “is hellbent on acquiring nuclear weapons.” Focus instead on purely practical questions. By any standards Iran is a tough nut to crack: it is nearly three times the size of Texas, with a population of 70 million and a big income from oil which the world cannot afford to lose. Iran is believed to have the ability to block the Straits of Hormuz in the Persian Gulf through which much of the world’s oil must pass on its way to market.

Keep in mind that the rising price of oil already threatens the world’s economy. Iran also has a large army and deep ties to the population of Shiite coreligionists next door in Iraq. The American military already has its hands full with a hard-to-manage war in Iraq, and is proposing to send additional combat brigades to deal with a growing insurgency in Afghanistan. And yet with all these sound reasons for avoiding war with Iran, the United States for five years has repeatedly threatened it with military attack. These threats have lately acquired a new edge.

President George W. Bush and Vice President Dick Cheney are the primary authors of these threats, but others join them in proclaiming that “all options” must remain “on the table.” The option they wish to emphasize is the option of military attack. The presidential candidates in the middle of this campaign year agree that Iran is a major security threat to the United States. Senator Hillary Clinton in the last days of April threatened to “totally obliterate” Iran—presumably with nuclear weapons—if it attacked Israel. Senator Barack Obama dismissed Clinton’s threat as “bluster” in the familiar Bush style but agrees that Iran cannot be permitted to build nuclear weapons, and he too insists that a US attack on Iran is one of the options which must remain “on the table.” The presumptive Republican candidate, John McCain, takes a position as unyielding as the President’s: Iran must abandon nuclear enrichment, stop “meddling” in Iraq with support for Shiite militias, and stop its sponsorship of “terrorism” carried out by Hezbollah in Lebanon and Hamas in Gaza. Any of these threatening activities, in McCain’s view, might justify a showdown with Iran.

Sometimes the President’s threats are chillingly explicit. In April the administration released details of the intelligence that explained an Israeli air strike last September on a large, blocklike building in which Syria, with the help…