Hahn was born at Großosterhausen (now part of Eisleben). He studied there, and then studied theology at the University of Leipzig and at Wittenberg. In 1819, he was nominated professor extraordinarius of theology and pastor at the Altstädtische Kirche in Königsberg in Prussia; and in 1820, he received a superintendency in that city. In 1822, he became professor ordinarius. In 1826, he became professor ordinarius of theology at Leipzig, where, hitherto distinguished only as editor of Bardesanes, Marcion (Marcions Evangelium in seiner ursprünglichen Gestalt, 1823), and Ephraem Syrus, and the joint editor of a Syrische Chrestomathie (1824), he came into great prominence as the author of the treatise De rationalismi qui dicitur vera indole et qua cum naturalismo contineatur ratione (1827), and also of an Offene Erklärung an die Evangelische Kirche zunächst in Sachsen und Preussen (1827), in which, as a member of the school of E. W. Hengstenberg, he endeavoured to convince the rationalists that it was their duty voluntarily and at once to secede from the Protestant churches.
