That opinions in religion are not matters of indifference, but have a definite bearing on the position of their holders in the Divine Sight, is a principle on which the Evangelical Faith has from the first developed, and on which that Faith has been the first to develop ... Faith is in this, as in other respects, a characteristic of the Gospel, except so far as it was anticipated, as its time drew near.... On the other hand, the Greek Philosophers were authoritative indeed in their teaching, enforced the "Ipse dixit," and demanded the faith of their disciples; but they did not commonly attach sanctity or reality to opinions, or view them in a religious light. Our Saviour was the first to "bear witness to the Truth," and to die for it, when "before Pontius Pilate he witnessed a good confession." St. John and St. Paul, following his example, both pronounce anathema on those who denied "the Truth" or "brought in another Gospel." Tradition tells us that the Apostle of love seconded his word with his deed, and on one occasion hastily quitted a bath because an heresiarch of the day had entered it. St. Ignatius, his contemporary, compares false teachers to raging dogs; and St. Polycarp, his disciple, exercised the same severity upon Marcion which St. John had shown towards Cerinthus.
... It seems to have been the duty of every individual Christian from the first to witness in his place against all opinions which were contrary to what he had received in his baptismal catechising, and to shun the society of those who maintained them. "So religious," says Irenæus after giving his account of St. Polycarp, "were the Apostles and their disciples, in not even conversing with those who counterfeited the truth."
Such a principle, however, would but have broken up the Church the sooner, resolving it into the individuals of which it was composed, unless the Truth, to which they were to bear witness, had been a something definite, and formal, and independent of themselves. Christians were bound to defend and to transmit the faith which they had received, and they received it from the rulers of the Church; and, on the other hand, it was the duty of those rulers to watch over and define this traditionary faith. .... "Polycarp," [Irenaeus] says when writing against the Gnostics, "whom we have seen in our first youth, ever taught those lessons which he learned from the Apostles, which the Church also transmits, which alone are true. All the Churches of Asia bear witness to them; and the successors of Polycarp down to this day, who is a much more trustworthy and sure witness of truth than Valentinus, Marcion, or their perverse companions. The same was in Rome in the time of Anicetus, and converted many of the afore-named heretics to the Church of God, preaching that he had received from the Apostles this one and only truth, which had been transmitted by the Church."