In 1780 he became an associate professor of
philosophy at the
University of Wittenberg, where he served as
rector in 1790–91. In 1792 he was appointed Oberhofprediger (first preacher) to the Saxon court in
Reinhard was one of the more influential Protestant ministers of his era, and was an important representative of "enlightened theological
supernaturalism". He was not opposed to contemporary rationalist thought, yet at the same time stressed the importance of divine supremacy and Biblical authority. In his sermons and lectures he attempted to establish the "truth of
Lutheranism" by rational means.
Reinhard was a prominent figure in the
Leben-Jesu-Forschung (Quest for the Historical Jesus) movement, a concept initiated by
Hermann Samuel Reimarus (1694-1768). He also exerted considerable influence upon the German educational system.