“For there must be also heresies: that they also who are approved may be made manifest among you.”

"The connection of the Father in the Son, and of the Son in the Paraclete [Holy Spirit], produces three coherent Persons, who are yet distinct One from the Other. These Three are one Essence [Substance], not one Person."

Tertullian against the Modalists c. AD 213

"For this is the reason why the Word of God was made man, and He who was the Son of God became the Son of man: that man, having been taken into the Word, and having received adoption, might become the son of God."

St. Irenaeus of Lyons against the Gnostics c. AD 180

"Whether Peter baptize or Paul baptize, it is Christ that baptizes. When Christ baptizes, even a wicked person can administer the Sacrament and yet the recipient receives the Sacrament validly. For the Sacrament does not belong to the giver, but to God who gives."

St. Augustine against the Donatists c. AD 400

It is necessary for the faithful to be instructed in the nature of heresy, that they may ever be vigilant against the snares of the enemy.  Heresy is defined as the obstinate denial or doubt, after the reception of baptism, of some truth which must be believed by divine and Catholic faith.  This deadly venom does not merely consist in error, but in a willful and persistent clinging to private judgment against the clear teaching of the Church, which is the pillar and ground of the truth, protected supernaturally by the Holy Spirit.

From the very beginning of the Apostolic age, this malice has assailed the Mystical Body of Christ.  Even as the wheat grows, the enemy sows the cockle (cf. Matt. xiii. 25), bringing forth pernicious doctrines that attempt to corrupt the purity of the deposit of faith.  The Arian outrage, the Nestorian division, the ravages of Protestantism, and the current distress wrought by dubious decisions from a Roman Curia of questionable faith have all been historical manifestations of this Satanic cunning, seeking to draw souls away from the sole Ark of Salvation.

The response of the Church, the Holy Roman Catholic Church, to such wicked uprisings has been a consistent manifestation of her divine protection and indefectibility.  When a heresy begins to spread, the Church, guided by the Holy Ghost, stirs up holy and learned men, the Fathers and Doctors of the faith, to clearly define the imperiled truth and refute the error through scripture and tradition.

As a final and definitive bulwark, the Church has historically convened Ecumenical Councils, wherein the truth is proclaimed with infallible authority, binding the consciences of all the faithful (cf. Matt xvi. 19).  Those who obstinately refuse this defined truth are then marked as outside the fold, and their doctrines are irrevocably condemned, thereby safeguarding the integrity of the faith and preserving the unity of the faithful Catholics against the deceitful innovations of the enemy.

However, it has also come to pass, in the most recent century, that the devil has increased in cunning and means with his limited assumptions as to the workings of the Holy Ghost, and has now proven to have seized even the time-honored and tested methods by which the Church had previously settled her disputes with heretics and deceivers. It is, rather, by these very means that he shall ultimately be undone, for as always, God’s Providence works through all manner of wickedness in order to bring about the maximum good, and nowhere shall this be more apparent (likewise revealing the inner workings of the minds and hearts of men) than where their obedience shall be exposed in its true adherence, thereby casting a light on those who merely profess with their lips the love of Christ, whilst forsaking the very foundations of faith, hope and charity that had been built up by His very Mystical Body.

Arius, departing from the rule of faith delivered by the Apostles, dared to deny the eternal Godhead of the Only-Begotten Son, asserting that He was created and not consubstantial with the Father. By this impiety he diminished the majesty of Christ and rendered the work of Redemption ineffectual, for no creature, however exalted, can restore fallen man to the friendship of the Almighty. Hence the Church, assembled at Nicaea under the guidance of the Holy Ghost, solemnly declared that the Son is “of one substance with the Father,” true God begotten from eternity, so that the faithful may understand that the salvation wrought upon the Cross proceeds from divine power, not from the efforts of a finite being.

Nestorius afterward erred grievously by dividing Christ into two persons, one divine and one human, thereby sundering the unity of Him who is both God and man. From this false division he further concluded that the Blessed Virgin could not rightly be called the Mother of God, as though she bore only a human son. The Church, instructed by the Apostolic tradition, condemned this teaching, affirming that the Word assumed a true human nature into the unity of His divine Person. Thus, the faithful profess with certainty that Mary is indeed the Mother of God, and that Christ the Lord, though possessing two distinct natures, remains one and the same Person, the eternal Son who deigned to be born of a woman for our salvation.

Eutyches, running to the opposite extreme, dissolved the sacred humanity of Christ into the divinity, as though His human nature were absorbed and no longer subsisted. By this error he undermined the reality of the Incarnation and the truth of the Redemption, for if Christ did not truly take our nature, He could not heal it nor offer Himself as the spotless Lamb for the sins of the world. Therefore the holy Council of Chalcedon, following the doctrine always preserved in the Church, taught that in Christ are two natures without confusion or change, united in one divine Person. In this confession the faithful behold the perfect Mediator, true God and true man, who alone is able to reconcile earth to heaven and restore mankind to the grace lost through sin.