Caspar Isenkrahe

Mathias Caspar Hubert Isenkrahe (12 May 1844, Müntz, Rhine Province – 12 August 1921, Trier) was a German mathematician, physicist and catholic philosopher of nature.

Caspar Isenkrahe grew up without a father, who died before Caspar's birth. Isenkrahe visited in 1856 the Progymnasium in Jülich, 1857 the Marzellengymnasium in Cologne and 1858 – 1863 the Realprogymnasium in Bonn. In 1868 he studied at the University of Bonn where he chose the subjects mathematics, physics, chemistry, mineralogy, botany, zoology, philosophy, Latin and German. On 31 July 1866 he made his PhD with an award-winning work about the anatomy of Helicina titanica, a species of snail. He became a teaching authority as a senior primary school teacher (pro facultate docendi) on 26 February 1869 for his chosen courses.

After a probationary year 1869/1870 at the high school of Bonn, he worked at the high school of Krefeld (at least to 1878) and then at the Realprogymnasium in Bonn. In the hope to be able to change to a high school career at the mathematical faculty at the University of Bonn he sent a habilitation document. The faculty approved his plan but it failed because of the Berlin government for reasons unconnected with the subject. A later attempt to receive a lectureship at the technical University of Braunschweig also failed. From 1893 to 1911 he was working as a high school professor at Trier until his retirement.

Until his death in 1921 he was actively engaged in the fields of mathematics, physics and natural philosophy. He corresponded with well-known mathematicians and physicists, such as Hermann von Helmholtz, Heinrich Hertz, Felix Klein and Philipp Lenard. Because of his unusual scientific creativity and versatility the philosophical faculty of the University of Bonn honoured him demonstratively on the occasion of his golden doctor anniversary with the renewal of his doctor dignity on 31 July 1916. Caspar Isenkrahe died after serious physical sufferings on 12 August 1921.

His legacy is kept safe in Trier (to be more precise partly in the town archives and partly in the diocese archives). The partial papers I (size: 0.5 meters) in the town archives of Trier includes correspondences, poems, clay creations, manuscripts as well as different collections from the cultural life around the time of the turn of 19th to the 20th century. The partial papers II (size: 2.50 meters) in the diocese archives includes personal documents, works, a biography as well as additional correspondence.

Isenkrahe always had a special inclination towards mathematics and produced a row of publications in the field of abstract mathematics. In particular his works around the theory of the prime numbers were appreciated.

The question of infinity fascinated him in the field of the Philosophy of nature.

As a physicist, Isenkrahe criticised the theories of gravitation of his time. Based on a Le Sage type model, which he developed independently, he presented an explanation of the phenomenon of gravity which was noticed by well-known physicists like Paul Drude, Walter Ritz and Arnold Sommerfeld.

As educationalist and religious Roman Catholic he felt obliged to give a proof of the existence of God on a natural philosophical basis. He also considered it to be necessary to examine the paranormal phenomena which were issued by the Roman Catholic Church as a 'miracle'. He dealt increasingly with experimental theology later.

In a book written in 1921 he tried to mediate in the debate around the theory of relativity, which had partly been led by both sides by scientifically inadmissible means.

• Wilhelm Bers (1944) „Professor Dr. phil. Caspar Isenkrahe aus Müntz bei Jülich – (1844–1921) “, Rur-Blumen 23, Nr. 16, Seiten 61 – 62.
• Wilhelm Alfred Miller, Isenkrahe-Bibliographie, 3. ergänzte Aufl., Berlin/Leipzig 1927.
• Adalbert Michael Bock, Die Theorie von Isenkrahe in ihrer Anwendung auf die Anziehung und Bewegung der Himmelskörper (Dissertation), München 1891.