Teaching creationism in science class as an alternative to evolution is inappropriate.

As my old professor Carl Sagan said so often, 'When you’re in love, you want to tell the world.’ And I base my beliefs on the information and the process that we call science. It fills me with joy to make discoveries every day of things I’ve never seen before. It fills me with joy to know that we can pursue these answers. It is an astonishing thing that we are — you and I are one of the ways the universe knows itself.

Our goal in science is to discover universal laws of nature. That pursuit fills me with wonder.

We should educate more women and girls. Because that is the surest route to controllably, manageably reducing the human population. Educated women have fewer kids. And the kids they do have are better cared for and are more successful. As I like to say, it's not one thing that we need to focus on. It's everything all at once.

What happens to other species also happens to us.

The most serious problem facing humankind is climate change.

To leave the world better than you found it, sometimes you have to pick up other people's trash.