Erich Kretschmann (1887–1973) was a German theoretical physicist whose work on Einstein’s General Theory of Relativity (1917) offered some interesting insights, but was also critical of Einstein’s semantics. Einstein responded in a paper in 1918 and agreed that Kretschmann’s criticism was valid. Kretschmann wrote his thesis under the supervision of Max Planck and obtained his doctorate in 1914. A psychiatric disease during his adolescence made him permanently unfit for military service and saved him from having to participate in the First World War. From 1920 he lectured in theoretical physics at the University of Königsberg. In 1926 he became an apl. professor, a position which he held until 1945. After his escape from Königsberg in January 1945 he found temporary accommodation at Rendsburg, Schleswig-Holstein. In 1946 he was appointed as a full professor of theoretical physics at the Martin-Luther-Universität Halle.