 While it is in the nature of philosophical movements and their leading doctrines to court controversy, the Vienna Circle and its philosophies did so more than most. To begin with, its members styled themselves as conceptual revolutionaries who cleared the stables of academic philosophy by showing metaphysics not simply to be false, but to be cognitively empty and meaningless. In addition, they often associated their attempt to overcome metaphysics with their public engagement for scientific Enlightenment reason in the ever-darkening political situation of 1920s and 1930s central Europe. Small wonder then that the Vienna Circle has sharply divided opinion from the start. There is very little beyond the basic facts of membership and its record of publications and conferences that can be asserted about it without courting some degree of controversy. (For English-language survey monographs and articles on the Vienna Circle, see Kraft 1950, Jorgensen 1951, Ayer 1959b, Passmore 1967, Hanfling 1981, Stadler 1998, Richardson 2003. Particularly rich in background and bio-bibliographical materials is Stadler 1997 [2015]. The best short introductory book has remained untranslated: Haller 1993. For popular overviews see Sigmund 2015 [2018] and Edmonds [2020].)