This chapter, as the prior one, will provide for detailed studies of the practice of QED during the 1930s. It will focus on the scattering of light by light, higher order calculations in radiation theory, the Delbrück effect and the theory of radiation damping. The historical study of light-by-light scattering will reveal another instance of what I called a “false prediction”, it will allow for a discussion of the rather curious terminology of “virtual possibilities”, which provides for a connection to the BKS theory, and it will exemplify the general algorithm of QED discussed in the previous chapter. Bernhard Kockel’s dissertation came with another instance of a “false prediction”, provided for a discussion of the exclusion principle for virtual entities and allows to compare the usefulness of the representational formats of tables and term scheme diagrams. The approaches to the Delbrück effect exemplify how specific ways of accessing a theory were upheld and how a “false prediction” can lead to the further evaluation of the formalism (in this case resulting in Furry’s theorem). Finally, the theory of radiation damping nicely demonstrates how the intermediate or “virtual” states could be manipulated by the historical actors. Its failure shows, that this could not be done at will. I will conclude this chapter with an analysis of the conceptual strands opened up in this and the prior chapter. It will bring together the most important conceptual results of the last two chapters.