History shows that societies where opportunity is safeguarded tend to be societies that are good international citizens.

No country can succeed if it denies itself the talents of half of its people.

Americans, for their part, must accept that a strong Europe will not be content to simply do America's bidding.

It is neither feasible nor desirable for Europe to establish itself as a geopolitical equal or competitor of the U.S.

In a global world, what happens within one country can all too easily affect others.

Russian membership in the World Trade Organization has the potential to strengthen the rule of law, combat corruption, and give Russia a stake in better relations with the outside world.

The benefits of freer trade, such as job creation, lower inflation, and greater consumer choice, are often invisible or only partly visible.

Weapons of mass destruction - nuclear, biological, and chemical weapons - are just that, and no cause can excuse their use.

The United States emerged from the Cold War with unprecedented absolute and relative power. It was truly first among unequals.

The decision to attack Iraq in March 2003 was discretionary; it was a war of choice.

There is no getting around the reality that the second Iraq war was a war of choice; had it been carried out differently, it still would have been an expensive choice and almost certainly a bad one.

Dissent is as American as cherry pie.

I did not support the U.S. decision to intervene with military force in Libya. The evidence was not persuasive that a large-scale massacre or genocide was either likely or imminent. Policies other than military intervention were never given a full chance.

Foreign policy must be about priorities. The United States cannot do everything everywhere.

America must reduce its fiscal deficit, modernize its infrastructure, and improve its schools.

On occasion, terrorists will succeed despite our best efforts. That is part of the legacy of 9/11. But 9/11 also shows us that while terrorists can destroy, they are unable to create.

If you assume away most or all of the questions or difficulties, you can persuade yourself of just about anything.

If anything, what happened in Iraq after the fall of Saddam set back prospects for democratic reform in the region, as many came to associate political change with chaos.

White House staff are meant to coordinate and set policy, not carry it out.

The first Iraq War was one of necessity because vital U.S. interests were at stake, and we reached the point where no other national-security instruments were likely to achieve the necessary goal, which was the reversal of Saddam Hussein's invasion and occupation of Kuwait.

There's a pattern in Bush 43's presidency of being attracted to the big and the bold, and my whole reading of him is that he was instinctively uncomfortable with what you might call a modulated foreign policy - a foreign policy of adjustment, of degree.

When great powers fade, as they inevitably must, it's normally for one of two reasons. Some powers exhaust themselves through overreach abroad, underinvestment at home, or a mixture of the two. This was the case for the Soviet Union. Other powers lose their privileged position with the emergence of new, stronger powers.

Donald Trump's United States is not isolationist. He has authorized the use of limited military force against the Syrian government in a manner his predecessor rejected.

Trump is the first post-World War II American president to view the burdens of world leadership as outweighing the benefits.

Trade accords had been a staple of the post-World War II world, providing a mechanism for economic growth, development, and association with friends and allies, and a means of reining in would-be adversaries who otherwise would have little incentive to act with restraint.

What is obvious is that Donald Trump is comfortable with an approach to running his presidency based on what worked for him in the private sector.

Any time you use military force, you have got to have a clear purpose that military forces can achieve.

I tend to be one of those who does not equate democratization with the holding of elections. The emphasis ought to be on such things as rule of law, economic reform, and promotion of a free media - in short, essentially independent, free institutions.

Vietnam was not a war of choice the United States had to fight. It was clearly not central.

For President Bush, the first, the 41st president, George Herbert Walker Bush, I spent all 4 years of his presidency on the staff for the National Security Council.

There is no way to know for certain what accounts for North Korean decisionmaking, given how closed a country it is.

No amount of sanctioning will persuade North Korea to give up nuclear weapons, nor will China step up and solve the problem for us.

How can we pressure China on North Korea if China's one of the two largest holders of American debt?

Our inability to govern ourselves at home, to deal with everything from infrastructure to our debt to tax policy, is reducing the appeal of the American model.

I did not believe in the Iraq war.

Campaigning and governing are two very different activities, and there is no reason to assume that how Trump conducted the former will dictate how he approaches the latter.

If you want to encourage some activity, make it easy.

Behavioral economics offers a plausible explanation for overreactions by the market. For example, a long period of bad performance can lead to stereotyping.

Whenever I'm asked to autograph a copy of 'Nudge,' the book I wrote with Cass Sunstein, the Harvard law professor, I sign it, 'Nudge for good.' Unfortunately, that is meant as a plea, not an expectation.

In the 1940s, economics started getting highly mathematical. It was basically because economists weren't smart enough to write down models of real behavior that they started writing down models of highly rational behavior - and they kind of forgot about humans.

The lesson of my field, behavioral economics, is that we need to understand the ways in which we differ from the rational human assumed in standard economic theory.

We all need a lot of humility, and especially about the economy.

Countries all around the world, starting with the U.K., have started behavioural insight teams, often referred to as nudge units. And they seem to be doing lots of good.

If you're not putting enough away for emergencies or retirement, making commitments in advance, such as signing up for payroll withholding, can help.

Real people have trouble balancing their checkbooks, much less calculating how much they need to save for retirement; they sometimes binge on food, drink, or high-definition televisions. They are more like Homer Simpson than Mr. Spock.

Arthur Laffer's idea, that lowering taxes could increase revenues, was logically correct. If tax rates are high enough, then people will go to such lengths to avoid them that cutting taxes can increase revenues. What he was wrong about was in thinking that income tax rates were already so high in the 1970s that cutting them would raise revenues.

Lotteries are just one way to provide positive reinforcement. Their power comes from the fact that the chance of winning the prize is overvalued.

I am all for trying to teach household finance in schools, starting as early as possible. And when it comes to high school, I think learning about compound interest is at least as important as trigonometry or memorizing the names of all 50 state capitals.

Leaders are important but not omnipotent.

If there is one thing that most economists agree about in the realm of tax policy, it is that it's best to broaden the base of any tax, all else being equal. That means minimizing the number of deductions and exclusions from taxable income in order to lower marginal rates and reduce distortions.