  During the three decades from 1930 to 1960 J. L. Doob was, with the possible
exception of Kolmogorov, the man most responsible for the transformation of the
study of probability to a mathematical discipline. His accomplishments were
recognized by both probabilists and other mathematicians in that he is the only
person ever elected to serve as president of both the IMS and the AMS. This
article is an attempt to discuss his contributions to two areas in which his
work was seminal, namely, the foundations of continuous parameter stochastic
processes and probabilistic potential theory.
