Introductory Note To S1929b And 1930b

Following an invitation of the Faculty of Mathematics and Sciences of the University ofWarsaw, Zermelo gave nine one-hour talks at theWarsaw Mathematical Institute between 27 May and 10 June 1929. On 24 May he gave an additional talk on the logical form of mathematical theories (1930b) to the Polish Mathematical Society and a further one on 7 June on reflection in analytical curves. The topics he treated in Warsaw range from a justification of classical logic and the infinite to a critical discussion of intuitionism and Hilbert’s proof theory, but he also dealt with specific topics such as a new notion of set or the (von Neumann) ordinals. Taken together, these talks provide a complete picture of his foundational views at this time and served as a platform from which he developed new insights when faced with the pioneering results of Thoralf Skolem and Kurt Gödel. Zermelo’s views had evidently been sharpened by intensive discussions with the philosopher Marvin Farber in the 1920s.