It was through his engagement with the program of logical analysis floated by Russell in 1915 that Carnap began to affect the shape of 20^th century philosophy. The program aimed at bringing to philosophy a certain method or attitude, resembling that of the sciences in its focus on progress in solving problems rather than on defense of doctrines. Progress brought with it the doctrinal flux that soon saw the phenomenalism of Carnap's Logische Aufbau der Welt ¹ yield to the physicalism of his Logische Syntax der Sprache ² and saw his early deductivism give way to the probabilism of his last 25 years, during which his work in semantics fostered a flowering of modal logic.³ He welcomed real progress and its attendant doctrinal flux from whatever source, others no less than himself. The celebrated "Death of Logical Positivism"⁴ refers to particular doctrines (e.g. phenomenological reductionism) and methods (e.g., syntax) that Carnap and his friends abandoned for reasons rooted in the program itself. Broadcasting out of Europe those of its participants and associates whom it did not kill, Nazi power propagated the movement, which grew and changed rapidly in response to hard challenges.