When U.S. Secretary of State Hillary Rodham Clinton recently broached the subject of Kim Jong Il's succession, she was criticized for speaking about a topic some thought was better left untouched. Clinton should indeed have refrained from talking about Kim's current health and future successor — not because the subject should be taboo but because it is probably irrelevant.

North Korea's behavior and nuclear ambitions are best understood by looking not at its admittedly bizarre leader but at its circumstances. Consider that there are 26,000 invasion-ready U.S. troops in South Korea, with 33,000 more in Japan. A leadership succession won't change that — or Pyongyang's desire to be relevant in the world. North Korea's international demeanor most likely will remain intact whenever Kim's successor takes charge.

When makers of foreign policy personify states, they view their opponents' moves as evidence of who they are, not of the pressures they face. This is the essential logic of what psychologists call the "fundamental attribution error," a cognitive bias whereby people attribute the actions of others to their dispositions rather than to their situations.

If the error enters into thinking about U.S. foreign policy, it means our assessments of future threats could be wildly off. By at first framing the "war on terrorism" as a hunt for Osama bin Laden, for example, President George W. Bush shifted attention from al-Qaida as a whole and left himself vulnerable to criticism that, with bin Laden still at large, his war was a failure.

Putting stock in individual leaders is usually a bad idea, and it was one of the Bush administration's fatal flaws. To Bush, an ally was trustworthy because its leader was, and an enemy was only as devious as its leader. Shortly after he entered office, he famously answered a reporter's question about whether he trusted then-Russian President Vladimir Putin by saying, "I was able to get a sense of his soul." As the U.S.-Russian relationship deteriorated over time, Bush's confidence appeared misplaced.

When it came to Saddam Hussein, the animosity was personal. "After all," Bush said in 2002, "this is the guy who tried to kill my dad." Because the U.S.-Iraq dispute morphed into the Bush-Saddam dispute, the decision to go to war was stripped of a rationality that perhaps would have called for more restraint.

Demonizing Saddam was a mistake Bush's father made too. During the Persian Gulf War, President George H.W. Bush referred to Saddam as "that lying son of a bitch" and called him "Hitler revisited."

Colin Powell, who was chairman of the Joint Chiefs of Staff at the time, found this tendency counterproductive. He later said he believed that it raised public expectations about toppling the regime, yet once the U.S. kicked Iraq out of Kuwait, Saddam was left in power. Powell wrote in his autobiography that "our plan contemplated only ejecting Iraq from Kuwait. It did not include toppling Saddam's dictatorship. . . . I thought it unwise to elevate public expectations by making the man out to be the devil incarnate and then leaving him in place." Instead of focusing on the dictator, Powell favored speaking of "the Iraqi regime." As George W. Bush's secretary of State, however, Powell employed just the sort of synecdoche he had once condemned; his 2003 United Nations testimony can be read as an anti-Saddam tract.

During their presidential campaigns, Barack Obama and Clinton both promised to abandon the misplaced idealism of the Bush years in favor of a less ideological and more pragmatic foreign policy. "It's an argument between ideology and foreign policy realism," Obama said.

As they begin to steer the ship of state back toward a more realistic course, Obama and Clinton could start by keeping interpersonal relations separate from international relations. In dealing with rogue states in particular, the Obama administration needs to focus less on individual leaders and more on the motivations underlying their actions.

With Iran, this means not waiting until June, when a new president is elected, to sit down at the bargaining table. Waiting just gives Iran more time to advance its nuclear program, and besides, any new Iranian leader will face the same domestic and international pressures as Mahmoud Ahmadinejad. And with North Korea, this means targeting the country's underlying feelings of insecurity — rather than fretting about which leader happens to be in power.

Stuart A. Reid is an assistant editor at Foreign Affairs. He wrote this commentary for the Los Angeles Times.