1. The word “mystery” is certainly one of the most important key-words of Christianity and its theology. Vatican I expressly declared (D 1816; cf. 1671- -3; 1795 f.) that there are mysteries properly so called which can only be known through actual revelation by God (against Gnosticism, Rationalism and Semi-Rationalism). It follows that revelation and faith cannot be superseded and abolished by philosophy and understanding. Vatican I also affirmed that, despite their abidingly mysterious charact…