"Most of the people that I deal with are human. So I've had a lot of experience with that." — Carl Sagan

For me, it is far better to grasp the Universe as it really is than to persist in delusion, however satisfying and reassuring.

I've written a number of books that have to do with the evolution of humans, human intelligence, human emotions.

No other planet in the solar system is a suitable home for human beings; it's this world or nothing. That's a very powerful perception.

The professed function of the nuclear weapons on each side is to prevent the other side from using their nuclear weapons. If that's all it is, then we've gotta as: how many nuclear weapons do you need to do that?