Expert in the German Art of the Middles Ages. Baum studied art history at the universities of Munich, Berlin and Tübingen, where he worked under Karl Voll and Heinrich Wölfflin. He completed his dissertation in Tübingen in 1905 on the churches of the architect Heinrich Schickhardt (1558-1634) under Konrad von Lange. Baum wrote his habilitation under Heinrich Weizsäcker in Technische Hochschule in Stuttgart. In 1911 his work on Ulmer Plastik um 1500, caught the attention of the scholars Paul Clemen, Jakob Falke and Philipp Halm (1854-1923) at the Technische Hochschule. He taught art history there until 1924. Except for voluntary service in World War I, Baum worked between 1908-23 first as an assistant and then conservator at the Wurtemberg Office for Historic Conservation (Württembergischen Amt für Denkmalpflege) and at the state museum in Stuttgart. Out of this work he published the catalog Deutschen Bildwerke des 10.-18. Jahrhunderts (1931). In 1924 Baum was called to be the director of the museum at Ulm. There he dedicated himself to the history of local art and artists. He married Emma Gruner (1893-1970), a protestant woman, in 1929. In 1930 he published the final volume in the series of Handbuchs des Kunstwissenschaft, which was the first survey of the history of paintings and sculpture of the north Alps in the Middle Ages. After his dismissal in 1933 he was invited by Johnny Roosval of the University of Stockholm to lecture in the Winter semester of 1935. His lectures were published in 1937 in Paris as La sculpture figurale en Europe à l'époque mérovingienne. Back in Stuttgart as a private art historian, Baum was arrested by the Gestapo in 1938 as a Jew and taken to the concentration camp at Welzheim. Authorities at a museum in Bern rescued him in 1939, enabling a move to Switzerland. He lived in Switzerland until the end of World War II working for the state archive in Lucerne researching medieval sculptors. In 1946 Baum returned to Germany at the invitation of the minister of culture Theodor Heuss (1884-1963). Baum was enlisted in the rebuilding of German castles between 1947-1952. In his research on medieval Bavarian art, Bauch analyzed the development of styles and iconography of the Middle Ages. Baum understood style questions as matters of time, dissociated from at the trend toward a "scientific approach to art" which became vogue in the 1920s (led by Kurt Gerstenberg, Wilhelm Pinder, Oskar Hagen, Eugen Kurt Fischer) which related artistic epochs to among other things, ethnic peoples. Chief among these in the speculation was the gothic, which Baum regarded as an element of the era, not of a people. Typical of the form-analytic generation of art historians, Baum, saw the development of art in the context of the culture and history of ideas, a notion he adopted from Jacob Burckhardt. In Zwölf deutsche Dome des Mittelalters (1955) he examined individual buildings and their sculptural decoration in the context of their respective social conditions in the cities and dioceses. The self-sufficiency of the German buildings were stressed, contrasting French and Italian reliance on the antique. The wall treatment became a key notion for Baum.
[dissertation:] Die Kirchen des Baumeisters Heinrich Schickhardt. Tubingen, 1905, published, Stuttgart: Druck von W. Kohlhammer, 1905; [habilitation:] Die Ulmer Plastik um 1500. Stuttgart: J. Hoffmann, 1911; Die Malerei und Plastik des Mittelalters. volume 2. Deutschland, Frankreich und Britannien. Wildpark-Potsdam: Akademische verlagsgesellschaft Athenaion, m.b.h. 1930; Baukunst und dekorative plastik der frührenaissance in Italien. Stuttgart: J. Hoffmann, 1920; La sculpture figurale en Europe à l'époque mérovingienne. Paris: Les éditions d'art et d'histoire, 1937; Romanische Baukunst in Frankreich. Stuttgart: J. Hoffmann, 1910, English: Romanesque architecture in France. London: W. Heinemann, 1912; Zwölf deutsche Dome des Mittelalters. Zürich: Atlantis Verlag, 1955; Deutsche Bildwerke des 10. bis 18. Jahrhunderts. Stuttgart: Deutsche Verlags-Anstalt, 1917.
Wendland, Ulrike. Biographisches Handbuch deutschsprachiger Kunsthistoriker im Exil: Leben und Werk der unter dem Nationalsozialismus verfolgten und vertriebenen Wissenschaftler. Munchen: Saur, 1999, vol. 1, pp. 27-31; Metzler Kunsthistoriker Lexikon. 2nd ed. Stuttgart: J. B. Metzler, 2007, pp. 13-16; Röttgen, H. Geschichte des Instituts für Kunstgeschichte der Universität Stuttgart . http://www.uni-stuttgart.de/kg1/geschichte.