Preface

Summary

Preface

When I was in graduate school, I had a debate with one of my professors on a seemingly meaningless issue. The question was whether it was more likely for two American Jewish individuals who knew one another but lived far apart to meet by chance in Israel or in New Jersey. I claimed that the probabilities of these two people meeting in Israel or New Jersey were roughly equal. Israel and New Jersey had similar populations (actually New Jersey’s population was slightly larger) and a similar area. Without any additional information, there was no way of differentiating between random processes operating in New Jersey and those operating in Israel.

The professor claimed that the probability of any two American Jews meeting in Israel was much higher than a chance meeting somewhere in New Jersey. I do not recall the entire argument, but part of it was that (a) Americans who did not live in New Jersey were a priori unlikely to visit a place in New Jersey unless they had a specific reason for doing so; (b) New Jersey residents had all of the United States and virtually the entire world open to them, so traveling around in New Jersey was not such an attractive proposition; however, (c) many American Jews made it a point to visit Israel. Taken together, these patterns of movement suggested that it was more likely for these imaginary individuals to meet in Israel than in New Jersey.