ABSTRACT
Probability theory provides a way, indeed a style, of thinking about such problems and situations. The classical theory has proved to be very useful even in domains that are far removed from gambling. Since the applications of probability theory are constantly expanding in range and depth, it is unlikely that anyone can supply models for all the situations that will arise in the future. Some probability theories are "subjective" and have a large degree of "personal probability" as an essential part. In view of the wide variety of applications of probability, past, present, and future, we will develop a sequence of models of probability, generally progressing from the simpler to the more complex as we assume more and more about the model. The increasing use of computers tends to make many people favor "computable" numbers as a basis for the development of probability theory.
