Leonard Nelson

In Nelson's early years, he studied in Französisches Gymnasium Berlin where mathematics and science weren't notable in that school. He was therefore privately tutored by mathematician Gerhard Hessenberg (1874–1925), and began reading the works of philosophers Immanuel Kant, Jakob Friedrich Fries, and Ernst Friedrich Apelts, which began to spark his interest in philosophy.[5]

In 1901, Nelson studied mathematics and philosophy in Heidelberg University for a short period of time, before going to the Humboldt University of Berlin from March 1901 – 1903. From 1903 to 1904, he worked with mathematicians and philosophers in the University of Göttingen, such as; his doctoral advisor Julius Baumann, David Hilbert, Felix Klein, Carl Runge, and his later rival Edmund Husserl.[5]

Nelson's work was a philosopher was most concerned with critical philosophy, attributed to Kant. It sets out to find a "critique" on science and metaphysics, similar to empiricism,[6] as things can only be true based on the perceptions and limitations on human minds. Kant's 1781 book Critique of Pure Reason (Kritik der reinen Vernunft) inspired Nelson to go down the path of critical philosophy, and later followed the works of post-Kantian philosopher Fries who had also followed Kant's work.[7]

Although his 1904 dissertation Jakob Fries and his Youngest Critics (Jakob Friedrich Fries und seine jüngsten Kritiker) was successful, he had trouble in his early academic years. One such failed dissertation was his Die kritische Methode und das Verhältnis der Psychologie zur Philosophie (The Critical Method and the Relationship of Psychology to Philosophy). Nelson continued defending Fries' philosophy and ideas by publishing a neue Folge (new series) of Abhandlungen der Fries'schen Schule (1904) with Gerhard Hessenberg and mathematician Karl Kaiser. It was here that Nelson and these same friends created the Jakob-Friedrich-Fries-Gesellschaft (Jakob Friedrich Fries Society) to promote critical philosophy.[7]

In 1922, Nelson founded the Philosophisch-Politische Akademie (Philosophical-Political Academy or PPA) as a "Platonic Academy" and non-profit association, which was abandoned soon after the Nazis banned it, but re-established in 1949. It still stands today for political discussions between philosophers and politicians,[8] and was supported financially by the Gesellschaft der Freunde der Philosophisch-Politischen Akademie (Society of Friends of the Philosophical-Political Academy or GFA).[9] They started working with an education center called Landerziehungsheim Walkemühle, founded in 1921 by a support of Nelson, progressive teacher Ludwig Wunder (1878–1949). Although Wunder left it shortly after in 1924, educator and co-worker of Nelson, Minna Specht, took over,[10] with the help of journalist and author Mary Saran.

Ready to form new ideas, Nelson founded the Neo-Friesian School in 1903, with some well-known members, such as:

• Rudolf Otto, philosopher (1869–1937)
• Gerhard Hessenberg, mathematician (1874–1925)
• Otto Meyerhof, biochemist (1884–1951)

Other notable people, such as philosopher Kurt Grelling and mathematician Richard Courant (student of Hilbert), joined after its foundation. A larger list of ISK members and similar can be seen in the list of Germans who resisted Nazism. In 1909 he habiliated at the University of Göttingen and became Privatdozent there. He later worked there as a professor from June 1919 until his death on 29 October 1927.[7][11][12]

The Internationaler Jugendbund (International Youth Federation or IJB) was founded in 1917 by Nelson and Minna Specht. In 1918, Nelson became a brief member of the Independent Social Democratic Party (USPD) before becoming a member of the Social Democratic Party (SPD) from 1923–1925, when he was ultimately excluded. As a result, together with Minna Specht, he founded the Internationaler Sozialistischer Kampfbund (ISK; "International Socialist Militant League") in 1925, merging it with the IJB by taking over its publishing label, Öffentliches Leben.[11]

The socialist journalist Willi Eichler succeeded Nelson as president of the ISK after his death. Eichler and Specht would both sign the 1932 "Urgent Call for Unity" (Dringender Appell für die Einheit) in the ISK's official newspaper, Der Funke. It called for Germany's Social Democratic Party (SPD) and Communist Party (KPD) to create a left-wing united front in order to thwart the Nazis.[13] After the Nazi's defeat in 1945, the ISK was merged with the SPD with the agreement met on 10 December 1945, between the chairman of the ISK (Will Eichler) and chairman of the SPD (Kurt Schumacher). However, the ISK continued to be active in the resistance against Nazism. A British affiliate of the ISK was created (lasted from the 1920s to the 1950s) in the United Kingdom called the Socialist Vanguard Group.

Among Leonard Nelson's students and political companions in the International Socialist Kampfbund were:[14]

• SPD politician Willi Eichler (1896–1971)
• Prime Minister Alfred Kubel (1909–1999)
• Journalist Fritz Eberhard (1896–1982), later member of the Parlamentarischer Rat

English translation: "Collected Writings in Nine Volumes". It was published by Paul Bernays and Felix Meiner Verlag (a German scientific publishing house in philosophy), in Hamburg 1970-1977;[17][23]

• Volume I: Die Schule der kritischen Philosophie und ihre Methode
• Volume II: Geschichte und Kritik der Erkenntnistheorie
• Volume III: Die kritische Methode in ihrer Bedeutung für die Wissenschaft
• Volume IV: Kritik der praktischen Vernunft
• Volume V: System der philosophischen Ethik und Pädagogik
• Volume VI: System der philosophischen Rechtslehre und Politik
• Volume VII: Fortschritte und Rückschritte der Philosophie von Hume und Kant bis Hegel und Fries
• Volume VIII: Sittlichkeit und Bildung
• Volume IX: Recht und Staat

• Ethische Methodenlehre. by Veit & Comp., Leipzig 1915
• Die Rechtswissenschaft ohne Recht. von Veit & Comp., Leipzig 1917.
• Die sokratische Methode. Vortrag, gehalten am 11. Dezember 1922 in der Pädagogischen Gesellschaft in Göttingen. In: Abhandlungen der Fries’schen Schule. Neue Folge.Hrsg. v. Otto Meyerhof, Franz Oppenheimer, Minna Specht. 5. Band, H. 1. Öffentliches Leben, Göttingen 1929, S. 21–78.
• Demokratie und Führerschaft. Öffentliches Leben, Berlin 1932.
• Ausgewählte Schriften. Studienausgabe. Hrsg. und eingeleitet von Heinz-Joachim Heydorn. Europäische Verlagsanstalt, Frankfurt 1974.
• Vom Selbstvertrauen der Vernunft: Schriften zur krit. Philosophie und ihrer Ethik. Hrsg. von Grete Henry-Hermann (Philosophische Bibliothek. Band 288). Meiner, Hamburg 1975.