Obama and McCain have different ideas about war. Neither may be able to prevent it.

Is war a permanent part of the human condition?

I’ve been interested in this question since high school, when an inspiring teacher named Dora Venit spent two years confronting me with the grotesque facts of history. It was not very long after the Holocaust, and the height of the Cold War.

The first raised unanswerable questions about human inhumanity; the second kept us in a constant state of fear.

Progress, which we had believed in for centuries, had thoroughly betrayed us. We had just discovered that the worst things can happen on an industrial scale, and now for the first time, we had the technical ability to destroy most life on earth. Two nations brandished nuclear arsenals at each other, and any day they might exchange almost laughable overkill.

We drilled in school, but we knew the truth: Crawl under the desk, put your head between your legs, and kiss your ass goodbye. I remember being scrunched up under that old hardwood desk, attached to the seat in front of you, its curved iron legs bolted to the floor, and knowing that even it would not protect me.

Many years later Ronald Reagan, whom I detested at the time, helped end that state of fear, and he did it in part by stepping up the belligerency. The USSR was an “Evil Empire,” there was no compromise with evil, and the answer to their threat was a hugely expensive “Star Wars” shield. Asked how the Cold War would end, he said, “We win and they lose.”

It did end in pretty much that way-we outspent them in the arms race until their economy collapsed-and immediately people were talking about the Pax Americana, the “peace dividend,” and even “the end of history.”

Anthropologists knew better. I remember talking at lunch with a group of colleagues shortly after the Soviet Union broke apart; we all agreed that now that the two superpowers were no longer squelching religious and ethnic hatreds, there would be an awful succession of little wars.

The fall of the Twin Towers, of course, was as great a watershed as the fall of the Berlin Wall, and history, smoldering in the intervening decade, caught fire again with a vengeance. Four days later, in a press conference, President Bush told a grieving nation, “We will find those who did it. We will smoke them out of their holes. We will get them running, and we’ll bring them to justice. There is a desire by the American people to not seek only revenge, but to win a war against barbaric behavior.”

In a radio address right after the press conference, he said, “Those who make war against the United States have chosen their own destruction…I will not settle for a token act. Our response must be sweeping, sustained and effective.” Soon after he called the war on terror a “crusade.” A war in Afghanistan toppled a tyranny but left enduring conflict. Iraq, Iran, and North Korea formed an “axis of evil” fomenting terrorism and brandishing new weapons of mass destruction. And, amid fear, grief, anger, and misunderstanding, the second Iraq war began.

Shakespeare, seeking words for a Marc Antony grieving over the “bleeding piece of earth” that was Julius Caesar, wrote, “Cry havoc! And let slip the dogs of war…”-as if war were a pack of vicious canines foaming at the mouth, and all we have to do to start one is loosen our grip on the leash.

John McCain describes himself as a warrior who does not like war. He would press on in Iraq until victory, then stay to protect the peace for up to a century. Barack Obama says he would withdraw a brigade a month starting in January. Hillary Clinton said that if Iran launched nuclear weapons against Israel, she would obliterate Iran; Obama called that reckless and said he would meet with Iran’s leaders without prior conditions.

These seem like pretty stark choices. But Obama is already backpedaling on his promise to meet with Iran’s dictator, and we may soon hear some second thoughts about troop withdrawal. Even Democrats returning from Iraq say that things are much better there, and that precipitous withdrawal would risk all that has been gained at great length and great sacrifice. Religious violence could tear the country apart.

Meanwhile, Iran’s relentless belligerence is running down an ominous clock, and the possibility of a pre-emptive strike against its nuclear installations–by Israel, the U.S., or both–is in the air. Obama promises to solve the world’s problems with words, not weapons. But the dogs of war are not kindergarten children, to whom you can say, “Use your words.”

Something about the process leading up to war is deeply engrained in human nature. Not just aggressiveness, but a potent blend of fear and grief take hold of the human spirit and individual will becomes a slave to collective mood.

Can this be averted? The answer history offers is: Sometimes. Is this one of those times? That is perhaps the most important question facing us, and neither McCain nor Obama knows the answer.