It’s a wonderful thing when you’re able to recognize it before the actual fall.
Yes, and it’s critically important at a societal level. Where nuclear weapons are concerned, or cyber insecurity or global environmental degradation including climate change, we need to wake up to these problems before there is direct evidence that we need to. Afterward it’s too late.

Dorothie and I, fortunately, woke up before the direct evidence of a divorce. As we looked at our relationship, starting in the summer of 1980, it took about a year for us to really dig down and look at it honestly. That’s another key problem we need to face: we don’t see ourselves very honestly, at either a personal or national level.

Since we’re talking about the Heidelberg Laureate Forum, which relates to mathematics and logic, I’ll add that we have to recognize the limits of logic. For a long time, I tried running my life, my marriage and the whole family on logic. That didn’t work very well, but I kept repeating the same failed experiment. Not very logical! — In my second year of graduate studies, my first year of marriage, I took a course where we learned about Gödel’s Incompleteness Theorem and some other seemingly paradoxical results. The mathematicians of the early twentieth century were trying to reach pure truth. They were trying to produce a system of logic that had no anthropomorphic qualities. – It was very beautiful and elegant and totally pure mathematics. But then Gödel proved that logic cannot prove everything that’s true. Any system of logic that is at all interesting is either incomplete in that you cannot prove all true theorems; or if you can prove everything that’s true, it will be inconsistent. You’ll be able to prove some things that are false. Here I was, trying to base my life on logic, and logic was telling me that logic is incomplete, literally. I came home and told Dorothie, ‘I feel like I’m having a mental breakdown. I feel like I built my life on logic and logic is not on a strong foundation.’ If I’d been truly logical, I would have given up trying to base my life entirely on logic. But, illogically, I persisted in that futile experiment for too many years and nearly ruined my marriage in the process.

With public key cryptography, Whit and I explored areas that people thought you couldn’t get to. My colleagues all told me I was crazy, initially, to work in cryptography, and then we not only did good work but explored totally new territory.

Was there a specific point in your life that led you to pursue a career as a scientist?
(Laughter) I’m laughing because when I was eight years old we were studying explorers in school, and I really wanted to be one. But somehow, in the depths of my soul, I knew I couldn’t be an explorer because I had to be a scientist. I didn’t know about engineering and mathematics as a profession or I would have included those. It’s really weird that I knew I had to be a scientist at such a young age. I don’t know how I knew that, I just did. There’s stuff in us that’s hard to explain. Dorothie has very nicely pointed out that I have become both a scientist and an explorer. With public key cryptography, Whit and I explored areas that people thought you couldn’t get to. My colleagues all told me I was crazy, initially, to work in cryptography, and then we not only did good work but explored totally new territory. — The same has been true of my work in international security and interpersonal relationships, totally new territory opened up for me. There are probably people who have gone as far as Dorothie and I, but I don’t know anyone else. Given my current goals in life, I couldn’t ask for a better partner than Dorothie on this voyage of discovery.

How did you and Whitfield Diffie come together?
That’s a great story. Whit had worked at the artificial intelligence lab here at Stanford before we met. He got so interested in cryptography and the AI lab couldn’t have him working solely on cryptography, so he quit his job and traveled around the country learning about cryptography. He stopped in New York, for example, and met with David Kahn who had written ‘The Codebreakers’ and had a fantastic library of the classic papers on cryptography. He stopped at IBM’s T.J. Watson Research Lab in Yorktown Heights, NY, where I had worked from 1968 to 1969 in my first job out of my PhD. Whit stopped there because IBM had started a cryptographic research effort, coincidentally when I was there. The man they brought in to start it was Horst Feistel. I wasn’t involved in IBM’s cryptographic research, but Horst and I were in the same department, so I had lunch with him, and even though I didn’t work in cryptography then, I learned a lot from Horst. IBM’s cryptographic research effort was the best unclassified work at the time Whit visited, in 1974. I had gone back there a few months earlier to give a talk and meet with people working on cryptography, and Alan Konheim was in charge of the group doing the cryptographic research effort. When I got there, I spoke with Feistel, Konheim and some of the others and they were a little bit down. They said a secrecy order had just been placed on them by the NSA and they couldn’t tell me very much. Prior to that, it had been a fairly open effort. Feistel had worked on classified cryptographic research before, so the NSA had a lot of say.