 As the "Catholic Encyclopedia" noted of him in 1913, "Dereser's combative character got him in trouble everywhere, and, though believing himself a good Catholic, he was imbued with a rationalistic, anti-Roman spirit", which made him "imbued with the shallow Rationalism of his time" and therefore "explaining away everything supernatural in Scripture and religion".This made all his writings "tainted" in the eyes of the Church authorities, though only one was placed on the "Index Librorum Prohibitorum" (see below) and that without the name of the author - testifying to the Church's appreciation of his talent, in spite of its dislike of his rationalism.His Profession was in Cologne on 18 October 1777.