The role Hans Hahn played in the Vienna Circle has not always been sufficiently appreciated. It was important in several ways. In the ftrst place, Hahn belonged to the trio of the original planners of the Circle. As students at the University of Vienna and throughout the fIrst decade of this century, he and his friends, Philipp Frank and Otto Neurath, met more or less regularly to discuss philosophical questions. When Hahn accepted his fIrSt professorial position, at the University of Czernowitz in the north east of the Austrian empire, and the paths of the three friends parted, they decided to continue such informal discussions at some future time - perhaps in a somewhat larger group and with the cooperation of a philosopher from the university. Various events delayed the execution of the project. Drafted into the Austrian army during the first world war" Hahn was wounded on the Italian front. Toward the end of the war he accepted an offer from the University of Bonn extended in recognition of his remarkable 1 mathematical achievements. He remained in Bonn until the spring of 1921 when he returm: d to Vienna and a chair of mathe matics at his alma mater. There, in 1922, the Mach-Boltzmann professorship for the philosophy of the inductive sciences became vacant by the death of Adolf Stohr; and Hahn saw a chance to realize his and his friends' old plan."

Die gesammelten mathematischen und philosophischen Werke von Hans Hahn erscheinen hier in einer dreibandigen Ausgabe. Sie enthalt samtli che Veroffentlichungen von Hahn, mit Ausnahme jener, die ursprtinglich in Buchform erschienen - dazu gehoren neben dem zweibandigen Werk tiber Reelle Funktionen auch die Einfuhrung in die Elemente der hdheren Mathematik, die er gemeinsam mit Heinrich Tietze schrieb, seine An merkungen zu Bolzanos Paradoxien des Unendlichen und mehrere Kapi tel fUr E. Pascals Repertorium der hdheren Mathematik. Nicht aufge nommen wurden auch die Buchbesprechungen von Hahn, bis auf seine Besprechung von Pringsheims Vorlesungen uber Zahlen- und Funktions lehre, die einen eigenen Aufsatz tiber die Grundlagen des Zahlbegriffs darstellt. Hahn war nicht nur einer der hervorragendsten Mathematiker dieses lahrhunderts: Sein EinfluB auf die Philosophie war auch hochst bedeut sam. Das kommt in der Einleitung, die sein ehemaliger Schiiler Sir Karl Popper fUr diese Gesamtausgabe geschrieben hat, deutlich zum Ausdruck. (Diese Einleitung ist der lctzte Essay, den Sir Karl Popper verfaBte. ) Hahn schrieb ausschlieBlich auf deutsch. Wir haben seine Arbeiten in Teilgebiete zusammengefaBt (was auch auf andere Art geschehen hatte konnen) und ihnenjeweils einen englischsprachigen Kommentar vorange stellt. Diese Kommentare, die von hervorragenden Experten stammen, be schreiben Hahns Arbeiten und ihre Wirkung."

The role Hans Hahn played in the Vienna Circle has not always been sufficiently appreciated. It was important in several ways. In the ftrst place, Hahn belonged to the trio of the original planners of the Circle. As students at the University of Vienna and throughout the fIrst decade of this century, he and his friends, Philipp Frank and Otto Neurath, met more or less regularly to discuss philosophical questions. When Hahn accepted his fIrSt professorial position, at the University of Czernowitz in the north east of the Austrian empire, and the paths of the three friends parted, they decided to continue such informal discussions at some future time - perhaps in a somewhat larger group and with the cooperation of a philosopher from the university. Various events delayed the execution of the project. Drafted into the Austrian army during the first world war" Hahn was wounded on the Italian front. Toward the end of the war he accepted an offer from the University of Bonn extended in recognition of his remarkable 1 mathematical achievements. He remained in Bonn until the spring of 1921 when he returm: d to Vienna and a chair of mathe matics at his alma mater. There, in 1922, the Mach-Boltzmann professorship for the philosophy of the inductive sciences became vacant by the death of Adolf Stohr; and Hahn saw a chance to realize his and his friends' old plan."

Like Descartes and Pascal, Hans Hahn (1879-1934) was both an eminent mathematician and a highly influential philosopher. He founded the Vienna Circle and was the teacher of both Kurt Goedel and Karl Popper. His seminal contributions to functional analysis and general topology had a huge impact on the development of modern analysis. Hahn's passionate interest in the foundations of mathematics, vividly described in Sir Karl Popper's foreword (which became his last essay), had a decisive influence upon Goedel. Like Freud, Musil and Schoenberg, Hahn became a pivotal figure in the feverish intellectual climate of Vienna between the two wars. Volume 1: The first volume of Hahn's Collected Works contains his path-breaking contributions to functional analysis, the theory of curves, and ordered groups. These papers are commented on by Harro Heuser, Hans Sagan, and Laszlo Fuchs. Volume 2: The second volume deals with functional analysis, real analysis and hydrodynamics. The commentaries are written by Wilhelm Frank, Davis Preiss, and Alfred Kluwick. Volume 3: In the third volume, Hahn's writings on harmonic analysis, measure and integration, complex analysis and philosophy are collected and commented on by Jean-Pierre Kahane, Heinz Bauer, Ludger Kaup, and Christian Thiel. This volume also contains excerpts of Hahn's letters and accounts by his students and colleagues.

Like Descartes and Pascal, Hans Hahn (1879-1934) was both an eminent mathematician and a highly influential philosopher. He founded the Vienna Circle and was the teacher of both Kurt Goedel and Karl Popper. His seminal contributions to functional analysis and general topology had a huge impact on the development of modern analysis. Hahn's passionate interest in the foundations of mathematics, vividly described in Sir Karl Popper's foreword (which became his last essay), had a decisive influence upon Goedel. Like Freud, Musil and Schoenberg, Hahn became a pivotal figure in the feverish intellectual climate of Vienna between the two wars. Volume 1: The first volume of Hahn's Collected Works contains his path-breaking contributions to functional analysis, the theory of curves, and ordered groups. These papers are commented on by Harro Heuser, Hans Sagan, and Laszlo Fuchs. Volume 2: The second volume deals with functional analysis, real analysis and hydrodynamics. The commentaries are written by Wilhelm Frank, Davis Preiss, and Alfred Kluwick. Volume 3: In the third volume, Hahn's writings on harmonic analysis, measure and integration, complex analysis and philosophy are collected and commented on by Jean-Pierre Kahane, Heinz Bauer, Ludger Kaup, and Christian Thiel. This volume also contains excerpts of Hahn's letters and accounts by his students and colleagues.

Like Descartes and Pascal, Hans Hahn (1879-1934) was both an eminent mathematician and a highly influential philosopher. He founded the Vienna Circle and was the teacher of both Kurt Goedel and Karl Popper. His seminal contributions to functional analysis and general topology had a huge impact on the development of modern analysis. Hahn's passionate interest in the foundations of mathematics, vividly described in Sir Karl Popper's foreword (which became his last essay), had a decisive influence upon Goedel. Like Freud, Musil and Schoenberg, Hahn became a pivotal figure in the feverish intellectual climate of Vienna between the two wars. Volume 1: The first volume of Hahn's Collected Works contains his path-breaking contributions to functional analysis, the theory of curves, and ordered groups. These papers are commented on by Harro Heuser, Hans Sagan, and Laszlo Fuchs. Volume 2: The second volume deals with functional analysis, real analysis and hydrodynamics. The commentaries are written by Wilhelm Frank, Davis Preiss, and Alfred Kluwick. Volume 3: In the third volume, Hahn's writings on harmonic analysis, measure and integration, complex analysis and philosophy are collected and commented on by Jean-Pierre Kahane, Heinz Bauer, Ludger Kaup, and Christian Thiel. This volume also contains excerpts of Hahn's letters and accounts by his students and colleagues.