Probability is the guide of life, and of death, too.

If we're going to live an ethical life, it's not enough just to follow the thou-shalt-nots. … If we have enough, we have to share some of that with people who have so little.

Pain is pain, and the importance of preventing unnecessary pain and suffering does not diminish because the being that suffers is not a member of our own species.

I don't think there's much point in bemoaning the state of the world unless there's some way you can think of to improve it. Otherwise, don't bother writing a book; go and find a tropical island and lie in the sun.

I honestly don't know, but if America continues to refuse to reduce its greenhouse gas emissions, I see a bleak future not only for American society, but for the world as a whole. This is a global problem that is not going away, and the United States is an obstacle to solving it.

In my world of the people who study war and defense issues, we simply did not talk about robotics. We do not talk about it because it's seen as mere science fiction. It's cold, hard, metallic reality.

Philosophy ought to question the basic assumptions of the age. Thinking through, critically and carefully, what most of us take for granted is, I believe, the chief task of philosophy, and the task that makes philosophy a worthwhile activity.