DEPOSIT OF THE FAITH. The word *deposito* (Greek *parádoxon*) occurs in the letters of St. Paul to Timothy (1 Tim. 6:20; 2 Tim. 1:14), in the writings of several Fathers, especially in Tertullian (*De praescriptione*, 25: PL 2, 37), in St. Vincent of Lérins (*Commonitorium primum*, 22: PL 50, 667 ff.); it definitively enters theological terminology from the end of the 16th century and is sanctioned by the Vatican Council, sess. III, cap. 4 (Denz-U, 1798 ff.).
In legal language, the term indicates a thing of which the depositary is not the owner but the faithful guardian. In ecclesiastical language, the term is used to designate the complete and integral divine Revelation, as contained in Sacred Scripture and divine-apostolic tradition. This is the theological concept of the deposit.
To the deposit of the faith belong only those truths that are part of public revelation, strictly obligatory for all the faithful, excluding private revelations, even if genuine. So that the deposit of the faith, entrusted to the Church, may always be preserved and transmitted faithfully, Jesus Christ instituted the living magisterium, endowed with the gift of infallibility, which belongs to the whole Church as “the pillar and ground of the truth” (1 Tim. 3:15), personally to Peter, the foundation of the Church (Mt. 16:18), and to his successors in the Roman primacy (v. POPE).
Therefore, to the pope and the bishops united with him belongs the right and duty to preserve the deposit of the faith, to explain it, defend it, determine its content and extent, adapting it to the needs of men and of the times. This immutable preservation of the deposit of the faith does not, however, prevent a real progress (v. DOGMA) in the knowledge of it on the part of individuals and of the Church as a whole, but always “in eodem dogmate, eodem sensu, eademque sententia” (Vatican Council, sess. III, cap. 4, Denz-U, 1800). Hence, the infallible definitions issued by the Church do nothing more than authentically declare that the truths proposed are contained in the deposit of Revelation, and are generally nothing more than more explicit declarations of what was less expressly contained in earlier formulas or definitions (cf. *Sum. Theol.*, 2a-2ae, q. 1, a. 9, ad 2; a. 10, ad 1).