By Gareth Evans

Václav Havel, the Czech playwright and dissident turned president, and Kim Jong Il, the North Korean despot, might have lived on different planets, for all their common commitment to human dignity, rights, and democracy. When they died just a day apart this month, the contrast was hard for the global commentariat to resist: Prague's prince of light against Pyongyang's prince of darkness.

But it is worth remembering that Manichaean good-vs.-evil typecasting - the kind to which former President George W. Bush and former Prime Minister Tony Blair were famously prone, and of which we have had something of a resurgence in recent days - carries two big risks for international policymakers.

One risk is that it limits the options for dealing with those cast as irredeemably evil. The debacle of the U.S.-led invasion of Iraq should have taught us the peril of talking only through the barrel of a gun to those whose behavior disgusts us.

Sometimes threats to a civilian population will be so acute and immediate as to make military intervention the only option, as with Moammar Gadhafi's planned assault on Benghazi. But more often it will be a matter of relying on less extreme measures, like targeted sanctions and threats of international prosecution, and on diplomatic pressure and persuasion.

Negotiating with the genocidal butchers of the Khmer Rouge was acutely troubling for those of us involved, but the talks secured a lasting peace in Cambodia. And it is only negotiation - albeit backed by good, old-fashioned containment and deterrence - that can deliver sustainable peace with Iran and North Korea.

The second risk of seeing the world in black and white is greater public cynicism, which makes ideals-based policy-making even harder. Expectations raised too high are bound to be disappointed: Think of former British Foreign Secretary Robin Cook's "ethical foreign policy" at the start of Blair's premiership.

Political leaders who make much of "values" are often most likely to stumble. Think of the lamentable response by Bill Clinton's administration to the Rwandan genocide in 1994.

Then there is Western governments' highly selective embrace of democracy when it results in the election of those (like Hamas) they find unacceptable; the unwillingness of almost every nuclear state to match its disarmament rhetoric with credible action; and the almost universal double talk on climate change.

But if double talk were an indictable offense, there would be few left to attend international summits. The task is neither to pillory nor to sanctify political leaders caught in these traps, but to reconcile what they will often see as hopelessly competing demands of moral values and national interests, and to find ways to get them to do more good and less harm.

A useful way forward in this respect may be to fundamentally rethink the concept of "national interest." To its two traditional dimensions, economic and strategic, there is a strong case for adding a third: every country's interest in being, and being seen to be, a good international citizen.

Actively helping to solve global public-goods challenges (like climate change, human-rights protection, international piracy, drug trafficking, cross-border population flows, and the elimination of weapons of mass destruction), even when there is no direct economic or strategic payoff, is not simply the foreign-policy equivalent of Boy Scout good deeds. Selfless cooperation on these issues can actually work to a country's advantage by boosting its reputation and generating reciprocal support: My help in solving your drug-trafficking problem today will increase the chances of your supporting my asylum-seeker problem tomorrow. And a story couched in these realist terms is likely to be easier to sell to domestic constituencies than one pitched as disinterested altruism.

Countries should pursue what the great international-relations scholar Hedley Bull called "purposes beyond ourselves": Our common humanity demands no less. But the real world is a place of gray shades, not black and white, and more often than not, the cause of human decency and security will be better served by recognizing and working around that constraint rather than challenging it head on.