 One was then left with simple type theory (and no need for the Axiom of Reducibility). But even the simple theory of types eventually fell out of favor as a foundational theory for mathematics—possibly because in the wake of the Byzantine ramified theory, no version of type theory could find favor among mathematicians themselves. Type theory was displaced by the newly emerging set theory due to Zermelo and Fraenkel, which mathematicians could recognize more easily as a formal codification of Cantorian mathematical practice. A definitive and richly detailed history of the reception and eventual demise of Russellian logicism can be found in Grattan-Guinness (2000). (The terminology of ‘sets’ was adopted in order to contrast these ‘safer’, paradox-free objects with the problematic classes of Frege’s inconsistent theory.) 