By comparing the intellectual and personal profiles of Moritz Schlick and Otto Neurath, the Vienna Circle's two main opposing intellectual figures, we can also gain a clearer sense of the basic features of this group. We can, in other words, trace out the pluralistic theoretical dynamic at work in this heterogeneous scientific circle, explore the material constituting its "psychogram" and "sociogram," and arrive at a typology of its underlying personal, conceptual, political, philosophical, and scientific elements.