Saudi Arabia isn't the enemy, but it is a problem. It could make so much positive difference in the Islamic world if it used its status to soothe Sunni-Shiite tensions and encourage tolerance. For a time, under King Abdullah, it seemed that the country was trying to reform, but now under King Salman, it has stalled.

I think we need to rethink a lot of business skills. In finance, for example, social impact bonds are potentially a way of providing capital for investments that save the public money in a context in which government often doesn't invest in things that would save it money.

The greatest problem is not with flat-out white racists, but rather with the far larger number of Americans who believe intellectually in racial equality but are quietly oblivious to injustice around them.

The best escalator to opportunity in America is education.

Every high school and college graduate in America should, I think, have some familiarity with statistics, economics and a foreign language such as Spanish. Religion may not be as indispensable, but the humanities should be a part of our repertory. They may not enrich our wallets, but they do enrich our lives. They civilize us. They provide context.

What use could the humanities be in a digital age? University students focusing on the humanities may end up, at least in their parents' nightmares, as dog-walkers for those majoring in computer science. But, for me, the humanities are not only relevant but also give us a toolbox to think seriously about ourselves and the world.

My take is that the optimal approach to food, for health and ethical reasons, may be vegetarianism.

I've always been interested in public health approaches because it seems to me we have this yearning for silver bullets, and that is not in fact how change comes about. Change comes through silver buckshot - a lot of little things that achieve results. That's a classic public health approach.

I took a gap year myself after high school and worked on a farm near Lyon, France. I stayed with the Vallet family, picked and packed fruit, and discovered that red wine can be a breakfast drink. That led to further travel as a university student.

During the Arab Spring, I learned all sorts of things from Twitter. I wouldn't necessarily trust that information, but it gave me ideas about questions to ask. You can really learn things from the wisdom of crowds.

Our world is enriched when coders and marketers dazzle us with smartphones and tablets, but, by themselves, they are just slabs. It is the music, essays, entertainment and provocations that they access, spawned by the humanities, that animate them - and us.

Dr. Ben Carson has the most moving personal narrative in modern presidential politics. His mother, one of 24 children, had only a third-grade education. She was married at age 13, bore Ben and his brother, and then raised the boys as an impoverished single mother in Detroit. As a young boy, Carson was a terrible student.

Wilderness trails constitute a rare space in America marked by economic diversity. Lawyers and construction workers get bitten by the same mosquitoes and sip from the same streams; there are none of the usual signals about socioeconomic status, for most hikers are in shorts and a T-shirt and enveloped by an aroma that would make a skunk queasy.

Beware of generalizations about any faith because they sometimes amount to the religious equivalent of racial profiling. Hinduism contained both Gandhi and the fanatic who assassinated him.