He was one of the first Jewish theologians to combine a university education with Talmudical training.
From 1828 until his death he was chief rabbi of the grand duchy of Weimar, residing first at Lengsfeld and later at Eisenach.
Although the measure had aroused great dissatisfaction among the Jews, he strictly enforced the decree of the government (June 20, 1823) ordaining that Jewish services should be conducted exclusively in the German language and that the reading in Hebrew of sections of the Bible should be followed by their translation into the vernacular.
Hess was a member of the three rabbinical conferences which (1844–46) convened at Brunswick, Frankfort-on-the-Main, and Breslau, and as such was an advocate of uncompromising radicalism.
He edited Der Israelit des Neunzehnten Jahrhunderts from 1839 to 1847, and, with Samuel Holdheim as co-editor, in 1847 and 1848.