Homegrown terrorists are a real problem for even the most modern, democratic societies.

There is a clear norm against the spread of nuclear weapons, but there is no consensus or treaty on what, if anything, is to be done once a country develops or acquires nuclear weapons.

Trade is the all-but-forgotten weapon in the battle against poverty, but it can provide more help to the poor than aid can.

The Internet, one of the great inventions of the modern Western world, has shown itself to be a weapon that can be used to incite and train those who wish to cause harm to that world.

It is in the interest of Americans to find out what those wanting to be president think about a wide range of challenges and what they might do about them. We should want to get their take on the wisdom of past decisions, what they agree and disagree with, and why.

September 11, 2001, was a terrible tragedy by any measure, but it was not a historical turning point. It did not herald a new era of international relations in which terrorists with a global agenda prevailed or in which such spectacular terrorist attacks became commonplace.

Terrorists and terrorism cannot be eliminated any more than we can rid the world of disease. There will always be those who will resort to force against innocent men, women, and children in pursuit of political goals.

Democracy requires an informed citizenry able to question its government.

American influence in the world depends on the ability to act with real capacity and set an example that others will want to follow. This all takes resources.

What countries must do to join the World Trade Organization is precisely what they must do to become productive and democratic: accept the rule of law, reduce corruption, and become open, accountable, and transparent.

Living with a nuclear North Korea could give its leaders the confidence to act more aggressively versus South Korea. It could also, over time, drive both South Korea and Japan, as well as countries farther afield such as Vietnam, to reconsider their non-nuclear postures. The stability of a critical region of the world would suddenly be in doubt.

In a world in which the United States does less, whatever set of calculations, other countries will tend to calculate - to move in one of two ways. Either they will assuage or, to use a more loaded term, appease the strongest power in the neighborhood with all the consequences of that, or they will determine to take matters into their own hands.

If old American alliance commitments don't count for as much, countries will, in some cases, then say, 'Well, we've got to militarize in certain ways and act more independently.'

For too long, America tolerated a 'democratic exception' in the Muslim Middle East. As long as governments were friendly and backed regional stability, there was no need for outsiders to encourage representative government.

Not every threat to America's national interests can be addressed with military power.

Black markets exist any time there is a profit to be made.

The political world is defined by relationships rather than transactions, and by numerous actors at home and abroad with independent power. Navigating such a world is difficult and precarious.

I am confident in saying that Oberlin did more for me than vice versa. I took a fantastic class in religion, which led me to archaeology, which got me to the Middle East, which led me to international relations, which launched me on my career.

Indeed, in foreign policymaking, inconsistency is often a virtue. I speak not of principles but of policy.

Diplomacy can and will matter; little is inevitable in international relations.

Unrestrained zeal to make the world better could make it worse. Promoting democracy must be undertaken with humility, care, and wisdom.

Speaking truth to power is actually a form of loyalty.

If Trump, for whatever reason, continues to coddle Russia, then Congress, the media, foundations, and academics should publicly detail the corruption that characterizes Putin's rule.

Success in foreign policy, as in carpentry, requires the right tools for the job.