While there can be no reasonable doubt either that the Christian churches from the very beginning were in possession of a definite and formulated symbol, or that this symbol was an amplification of the trinitarian formula of Baptism, yet we are unable to ascertain with any degree of certainty what its exact original wording was. There has not been found in the early Christian writers a single passage recording the precise form of the baptismal confession or the rule of truth and faith as used in the earliest churches. This lack of contemporal written records is accounted for by the fact that the early Christians and Christian churches refused on principle to impart and transmit their confession in any other manner than by word of mouth. Such was their attitude, not because they believed in keeping their creed secret, but because they viewed the exclusively oral method of impartation as the most appropriate in a matter which they regarded as an affair of deepest concern of their hearts. It is universally admitted, even by those who believe that the apostles were instrumental in formulating the early Christian Creed, that the wording of it was not absolutely identical in all Christian congregations, and that in the course of time various changes and additions were made. "Tradition," says Tertullian with respect to the baptismal confession, received from the apostles, "has enlarged it, custom has confirmed it, faith observes and preserves it." (Zahn, 252. 381.) When, therefore, Tertullian and other ancient writers declare that the rule of faith received from the apostles is "altogether one, immovable, and irreformable," they do not at all mean to say that the phraseology of this symbol was alike everywhere, and that in this respect no changes whatever had been made, nor that any clauses had been added. Such variations, additions, and alterations, however, involved a doctrinal change of the confession no more than the Apology of the Augsburg Confession implies a doctrinal departure from this symbol. It remained the same Apostolic Creed, the changes and additions merely bringing out more fully and clearly its true, original meaning. And this is the sense in which Tertullian and others emphasize that the rule of faith is "one, immovable, and irreformable." The oldest known form of the Apostles' Creed, according to A. Harnack, is the one used in the church at Rome, even prior to 150 A.D. It was, however, as late as 337 or 338, when this Creed, which, as the church at Rome claimed, was brought thither by Peter himself, was for the first time quoted as a whole by Bishop Marcellus of Ancyra in a letter to Bishop Julius of Rome, for the purpose of vindicating his orthodoxy. During the long period intervening, some changes, however, may have been, and probably were, made also in this Old Roman Symbol, which reads as follows:--