Helmut Herbert Hermann Rehbein was born in Potsdam, Germany, on 15 February 1913, the son of Hermann Carl Heinrich Rehbein, a government clerk, and his wife, Martha Lucie Hedwig Haupt. In 1919 the family moved to Berlin and Helmut attended school in Lichterfelde. From 1931 to 1935 he studied theology at the University of Berlin under Alfred Bertholet, Wilhelm Lütgert, Leonhard Fendt and the great historian Hans Lietzmann. He read widely in literature and philosophy, but was especially influenced by the theologian Rudolf Bultmann.
He studied for the ministerial exams of the Confessing Church in 1936 and 1938. (This was a courageous choice as it opposed the pro-Nazi German Christian church.) He attended their seminary in Wuppertal–Elberfeld, and also served as an assistant in several parishes. He wished to marry Renate Jaeger, a solicitor’s daughter, but her mother was Jewish and they were forced to flee separately and secretly to London. Rehbein went through Switzerland. They were married in a civil ceremony on 14 February 1939 at Edmondton, London, and then in St George’s Lutheran Church, Whitechapel.
The couple were brought to New Zealand, just before war began, by the Presbyterian church. It decided that a parish appointment was risky and employed Helmut as a temporary tutor in the Theological Hall at Knox College, Dunedin, until he gained tenure in 1947. His remarkable intellectual and teaching gifts impressed many students and ministers, who were introduced to the best European scholarship. Helmut and Renate changed their surname to Rex in 1946, as part of their commitment to becoming New Zealanders, and in 1948 he gained an MA from the University of Otago for his work on Kierkegaard. A discerning critic of local culture, he reminded his students that there was more to their heritage than Scottish Presbyterianism. Deeply sympathetic to Maori and their culture, he was an important contributor to the decision in 1952 to grant the Presbyterian Maori synod formal powers. In the following year he attended a meeting in Tauranga to plan a college in Whakatane to educate Maori students for the ministry in their own cultural context.
Although his health was frail, he spoke impressively at ministers’ refresher schools and at conferences of the New Zealand Student Christian Movement. None of his colleagues had his gift for working in depth across disciplines and opening up new perspectives. In 1950 he began annual introductions to notable novels, and in 1955 he pioneered (in New Zealand) hermeneutics, the study of the procedures by which sacred texts are explained. He also gave a superb introduction to church history over a three-year cycle, the last of which was from 1958 to 1960. In 1953 he became the first professor of church history at the Theological Hall, and in 1954 he completed a doctorate in theology from Tübingen university after presenting a dissertation on St Paul’s ethics and eschatology.
Serious illnesses in 1956 and 1961 brought Rex close to death, but gave him a new understanding of life, movingly described in a letter to Bultmann. Briefly dean of theology at the University of Otago in 1963, he played a vital part in setting up a lectureship in the phenomenology of religion, which pioneered the study of religion in New Zealand universities. Illness forced his resignation in the same year and he led a very reclusive life until his death in Dunedin on 16 March 1967. He had finished Did Jesus rise from the dead? in September 1966, but did not live to see it published. In it he held that an affirmative answer is essential to Christian faith. Brief and profound, it demonstrated his outstanding scholarship and ability to throw fresh light on controversial matters. He had earlier published an introduction to hermeneutics (1958) and contributed to Christians in a secular society (1955). He wrote several articles for Landfall on individual freedom, existentialism and Christianity in the Roman Empire and reviewed in it Problems of religious knowledge by Peter Munz. He was influential and well known among New Zealand intellectuals.
Rex’s passion for self-understanding seemed strange to some students and colleagues, but his pastoral insights into racism, homosexuality and alcoholism were invaluable when such issues were rarely discussed constructively. His early death was a tragedy, for he transcended the division between liberals and conservatives, which had debilitated New Zealand churches, by striking his own path amidst the best international theologians. His wife, a librarian, who had cared for him devotedly, committed suicide in June 1968. They had had no children and their estate provided an educational trust named after him.