I do think there are certain times we should infringe on your freedom.

The estate taxes, on balance, are good. They get people to give money to charity, and they prevent these family dynasties which keep other people from having opportunities. It may be good for a family, but for society it's probably not good. And I've always been in favor of having an estate tax.

Most people won't have opportunity to do full-time service, but those lucky enough to have monetary wealth or some spare time really can make an enormous difference. As someone who's now in the public sector, and is seeing up-close-and-personal the real impact of what we do and what we give, I can tell you: every dollar and every volunteer help, in more ways than you can count.

Fighting climate change isn't just an obligation we owe to future generations. It's also an opportunity to improve public health - and drive economic growth - in the here and now.

The system [in U.S.] is designed for a two-party system. And those two parties have an interest in keeping third parties out. There's too much of the structure that works in the two-party way. They will keep the third party out.

To a contrarian like me, constant advice not to do something almost always starts me quickly down the risky, unpopular path.

There's a fascinating statistic: One out of every four people in America has visited New York since 9/11. It is astounding. Now, I don't know how you count it; it's some people coming multiple times.