Carl has a keen sense of humor, an incisive intelligence. He's just as intelligent in his speaking as he is in his writing….

I've learned a great deal from his articles. I like to think I have read just about everything he has written. Virtually everything I know about the possibility of extraterrestrial life was inspired by his writings on the subject. On that question our minds have the same set. I find it very easy to agree with Carl.

I don't agree with those who criticize him as a popularizer. I happen to think that the popularization of science is the most important thing a scientist can do, next to actually broadening science itself.