In 1970, as a 26 year-old, I joined in the effort in my home state of Massachusetts to organize for Earth Day. But what made the event so successful was that I was only one of about 20 million Americans of all ages and backgrounds who got involved.

President Obama and I both believe we don't have time for a meeting anywhere of the Flat Earth Society.

It's not normal that, when you close your eyes and listen to the news, too often the political back-and-forth in America sounds too much like it does in the kinds of countries that the State Department warns Americans not to travel to.

The Paris Agreement's going to continue without the United States of America.

For sure, there are times when one may have no choice but to go to war, but it is never something to rush to or accept without exploring every other available option.

You can't let concerns stop you; they drive you and they motivate you.

War should be not a war of choice; it should be a war of necessity. And it should be a last resort.

One of the most cherished photographs in my life is a picture of me with John Lennon - who I met back in 1971 at an anti-war rally.

My favorite album is 'Abbey Road.' I love 'Hey Jude.'

If you've ever played golf, you know that you yell 'fore' off the tee. You're not threatening somebody; you're warning them: 'Look, don't get hit by the ball, it's coming.'