In 1949, Richard Feynman (1918–1988) published the essentials of his solution to the recalcitrant problems that plagued quantum theories of electrodynamics of his days (Feynman 1949a). The main problem was that the theory, that was considered to be correct and often led to correct observable consequences, also implied that some quantities should be infinite, while by common sense or empirical evidence they were finite. Feynman devised a method of solving the relevant theoretical equations in which particular combinations of elementary solutions yielded empirically adequate results even when applied to complex problems. The combination of the basic solutions was guided by relatively simple graphical considerations as to how the elements that represented elementary interactions of electrons and light quanta could be put together to form a complex diagram.
Much of Feynman’s method relied on a diagrammatic representation of the physical processes as well as, at the same time, of the...