Catechesis
On-Going Instruction in the Principles of Christianity

2020 Jubilee 2021
YEAR OF THE EUCHARIST - 8/16

MYSTERIUM FIDEI
("MYSTERY OF FAITH",
ENCYCLICAL LETTER OF
POPE PAUL VI)

The Church, therefore, with the long labor of centuries and, not without the help of the Holy Spirit, has established a rule of language and confirmed it with the authority of the Councils. This rule, which has more than once been the watchword and banner of Orthodox faith, must be religiously preserved, and let no one presume to change it at his own pleasure or under the pretext of new science. Who would ever tolerate that the dogmatic formulas used by the ecumenical Councils for the mysteries of the Holy Trinity and the Incarnation be judged as no longer appropriate for men of our times and therefore that others be rashly substituted for them? In the same way it cannot be tolerated that any individual should on his own authority modify the formulas which were used by the Council of Trent to express belief in the Eucharistic Mystery. For these formulas, like the others which the Church uses to propose the dogmas of faith, express concepts which are not tied to a certain form of human culture, nor to a specific phase of human culture, nor to one or other theological school. 

No, these formulas present that part of reality which necessary and universal experience permits the human mind to grasp and to manifest with apt and exact terms taken either from common or polished language. For this reason, these formulas are adapted to men of all times and all places. But the most sacred talk of theology is, not the invention of new dogmatic formulas to replace the old ones, but rather such a defense and explanation of the formulas adopted by the Councils as may demonstrate that divine Revelation is the source of truths communicated through these expressions.

It must be admitted that these formulas can sometimes be more clearly and accurately explained. In fact, the achievement of this goal is highly beneficial. But it would be wrong to give these expressions a meaning other than the original. Thus the understanding of the Faith should be advanced without threat to its unchangeable truth. It is, in fact, the teaching of the First Vatican Council that “the same signification (of sacred dogmas) is to be forever retained once our Holy Mother Church has defined it, and under no pretext of deeper penetration may that meaning be weakened.”