The Catholic Church possesses one and the same faith throughout the whole world, as we have already said (Against Heresies 1:10 [A.D. 189]).
Since therefore we have such proofs, it is not necessary to seek the truth among others which it is easy to obtain from the Church; since the apostles, like a rich man [depositing his money] in a bank, lodged in her hands most copiously all things pertaining to the truth: so that every man, whosoever will, can draw from her the water of life.
For she is the entrance to life; all others are thieves and robbers.
On this account we are bound to avoid them, but to make choice of the things pertaining to the Church with the utmost diligence, and to lay hold of the tradition of the truth. For how stands the case? Suppose there should arise a dispute relative to some important question among us. Should we not have recourse to the most ancient churches with which the apostles held constant intercourse, and learn from them what is certain and clear in regard to the present question? For how should it be if the apostles themselves had not left us writings? Would it not be necessary [in that case] to follow the course of the tradition which they handed down to those to whom they did commit the churches? (ibid. 3:4).