There exist some excellent technical reviews of relativistic dispersion relations (Goldberger, 1960, 1961; Jackson, 1961), as well as Goldberger's (1970) own informal recollections of the period from about 1954–69. In addition, Cini (1980) and Pickering (1989a) have written about some of the sociological influences on that program. We shall comment on these later in this chapter and in the concluding chapter. However, let us begin with a few general observations about the mood of theoretical physics in the United States just after the Second World War, at least in one Physics Department, namely the University of Chicago. This is relevant for what follows, since that Department became a center of activity for the dispersion theory program. Wentzel and Fermi were on the faculty then and Goldberger and Chew were graduate students there. One frequent attendee at the theory seminars at Chicago during those years recalls that at that time (around 1948) the general spirit of many of the younger, exceptionally gifted theorists was that physics was something to do (never mind studying the works of the great masters) and that nothing significant had been done (in their areas of interest) prior to this. In fact, many other people had worked on these problems (e.g., fixed-source field theory) before, but there was little sense of history among the younger generation. Wentzel's comments (say, from the audience at a talk) on the previous literature were typically received with impatience.