The German interpreter of religion Louis Karl Rudolf Otto (1869-1937) found a thread of unity among all religions while resisting attempts to account for religion in non-religious terms such as the moral, the rational, and the aesthetic.

Born in Peine (Hanover), Germany, in 1869, Rudolf Otto was educated at Erlangen and Göttingen and taught at the Universities of Göttingen and Breslau before becoming professor of systematic theology at the University of Marburg in 1917. In that same year he published Das Heilige (translated as The Idea of the Holy), one of the most significant books in religion in the first half of the 20th century. Illness forced his early retirement in 1929, and he died in 1937 of arteriosclerosis and physical/psychological consequences of a serious fall.

His life and work spanned a tempestuous period in the religious and political history of Germany: World War I, the Treaty...