[2] In 1674 Duke John Frederick called him to Hanover as director of the consistory after Justus Gesenius († 1673).
As a disciple of Calixtus during the Syncretistic Controversy, Molanus used his power to abolish the hostility which prevailed between the Lutherans and the Reformed.
He was very active in aiding the Reformed, who after their expulsion from France by the revocation of the edict of Nantes (1685) found a refuge in the country of Hanover.
But he did not regard the Council of Trent legitimate because the Protestants had been condemned without being heard, and because it had not been accepted by the entire Catholic Church.
On account of the spirit of conciliation which Molanus manifested in these negotiations, it was rumored that he had become Roman Catholic, and he had to defend himself publicly in letters and treatises.