One can either debate the sociology of philosophical knowledge or one can do it (cf. Shapin 1982, p. 157). I have done it, that is, presented a case study in the sociology of philosophical knowledge, in a book entitled Psychologism (1995a). There I tell the story of the fall of naturalistic philosophy in Germany between 1880 and 1920. My treatment of this key episode in the history of twentieth-century philosophy is sociological, in that I focus as much on sociopolitical factors as I analyze philosophical arguments. I consider not only the philosophical writings of, say, Frege, Husserl, Erdmann, Sigwart, and Wundt, amongst others, but also professional interests, struggles over professorial chairs, wars, and mentalities. I shall summarize this case study below. In the second, main part of this chapter, however, I wish to debate, that is, justify or defend rather than do, the sociology of philosophical knowledge.