After a short period of study in Paris on the French Revolution, he spent some time working in the archives of Baden and Bavaria, and published in 1845 Die Geschichte der rheinischen Pfalz, which won for him a professorship extraordinarius at Heidelberg.
In 1835 he became Repetent, in 1838 Privatdozent and in 1841 professor extraordinarius in the theological faculty at Erlangen.
Here in 1 754 he became professor extraordinarius of theology, and three years later received an ordinary professorship. He lectured on dogmatics, church history, ethics, polemics, natural theology, symbolics, the epistles of Paul, Christian antiquities, historical theological literature, ecclesiastical law and the fathers, and took an active interest in the work of the Gottinger Societdt In 1766 he was appointed professor primarius.
Resigning in 1882 owing to conscientious scruples, he became professor extraordinarius of oriental languages in the faculty of philology at Halle, was elected professor ordinarius at Marburg in 1885, and was transferred to Gottingen in 1892.
His eldest SOH, Heinrich August Hahn (1821-1861), after studying theology at Breslau and Berlin, became successively Privatdozent at Breslau (1845), professor ad interim (1846) at Konigsberg on the death of Heinrich Havernick, professor extraordinarius (1851) and professor ordinarius (1860) at Greif swald.
He was, in 1742, named professor extraordinarius of ancient literature in the university of Leipzig, and in 1756 professor ordinarius of rhetoric. In the same year he received the degree of doctor of theology, and in 1759 was appointed professor ordinarius in the faculty of theology.
In 1853 he became professor extraordinarius of theology at Leiden, and in 1855 full professor.
Meanwhile his lectures and publications (among the latter a Grundriss der Neutestamentlichen Hermeneutik, 1816) had brought him into considerable repute, and he was appointed professor extraordinarius in the new university of Bonn in the spring of 1818; in the following autumn he became professor ordinarius.