Paul Moritz Cohn FRS[1] (8 January 1924 – 20 April 2006) was Astor Professor of Mathematics at University College London, 1986–1989, and author of many textbooks on algebra.

His father fought in the German army in World War I; he was wounded several times and awarded the Iron Cross.

After her death in October 1925, the family moved to a rented flat in a new building in Lattenkamp, in the Winterhude quarter.

He attended a kindergarten then, in April 1930, moved to Alsterdorfer Straße School.

[7] On the night of 9/10 November 1938 (Kristallnacht), his father was arrested and sent to Sachsenhausen concentration camp.

[5][7] He received a B.A in Mathematics from Cambridge University in 1948 and a Ph.D. (supervised by Philip Hall) in 1951.

He held several visiting professorships, in America, Paris, Delhi, Canada, Haifa and Bielefeld.

[4][6] In the early 1980s, funding cuts caused the closure of the small colleges of the University of London.

Cohn moved to University College London in 1984,[10] together with the two other experts at Bedford on ring theory, Bill Stephenson and Warren Dicks.

He retired in 1989, but remained active as professor emeritus and honorary research fellow until his death.

[3][5] He was president of the London Mathematical Society, 1982–1984, having been its secretary, 1965–1967 and a council member in 1968–1971, 1972–1975 and 1979–1982.

He generalised a theorem due to Wilhelm Magnus, and worked on the structure of tensor spaces.

After that, he moved into the areas of Jordan algebras, skew fields, and non-commutative unique factorisation domains.

Cohn wrote a subsequent revised iteration of the first volume as Classical Algebra (Wiley, 2000) as a more "user friendly" version for undergraduates (according to its preface); this book also includes a few selected topics from volumes II and III of Algebra.