How would my career have been different without John Nash? What a wonderful question! My difficulty in answering it is an indication of how influential he has been in everything that I have done. I wanted to be a mathematical social scientist since I was 12 years old, when I read Isaac Asimov’s science-fiction novel Foundation. But my concept of what kinds of mathematical models should be studied was completely transformed when I read Nash’s and Harsanyi’s papers in college.