I have been told that an author loses half the readers with every equation. If that is so, and if every person on the globe started to try to read this book, I have a reader left! My thanks and congratulations, lonely reader.

Actually, I am not that pessimistic. It seems more likely to me that you lose half your readers on the first, one-third on the second, and so on. Some hardy souls will persevere. They may even expect mathematics. And we are at the end.

But we do not need to be. I have barely touched the surface of every topic that has been discussed. Specialists in each field may curse me for having given so light a treatment of their topic. Those same specialists may grouse about my having spent so much time talking about things outside of their interests. All I can say to the reader is that if you want to go further, go to the specialty literature. I am not being snooty; I really hope that some readers will want to take these chapters further.

I knew when I started that I would have to omit some topics, for there are so many applications of mathematics in the social sciences – well beyond statistics – that it would take volumes to cover them all. I mean that literally. The series Mathematical Psychology, which covered psychology alone, ran to three full volumes … in 1963! Things have happened in the intervening 40-plus years.