Heresy refers to an opinion that is in opposition to the authorized teachings of any church and promotes separation from the main body of the faithful believers. In the Catholic Church, heresy refers to any baptized Catholic who denies or doubts any truth which is part of the Divine Deposit of Faith or revelation and therefore must be believed. Formal denial can lead to excommunication. Canon 1364 states, “An apostate from the faith, a heretic or a schismatic incurs a latae sententiae excommunication.”
“Heresy” is from the Greek word for “faction.” Heresy has existed since the foundation of the Church. In 2 Corinthians 11:13 we hear Paul stating, “For such men are false apostles, deceitful workmen, disguising themselves as apostles of Christ.” Again in John’s letters, 1 John 2:19 we hear, “They went out from us, but they were not of us; for if they had been of us, they would have continued with us; but they went out, that it might be plain that they all are not of us.” Finally, Peter admonishes in 2 Peter 2:1, “False prophets also arose among the people, just as there will be false teachers among you, who will secretly bring in destructive heresies, even in denying the Master who bought them, bringing upon themselves swift destruction.”
Heresy can be stopped by listening to the authentic teaching authority of the Church, the magisterium. The magisterium is made up of the pope and the bishops when they are united with the pope or when they teach the constant teachings from the Sacred Deposit of Faith. The Holy Spirit has given the awesome gift of infallibility to the pope when he teaches in matters of faith and morals. Infallibility is that gift that preserves the pope from error. This is important so that every generation to the end of time will be guided by the uncorrupted truth on the pathway to heaven.
There were many heresies that existed in the early church which lasted until the Middle Ages. Some heresies resurface and are given new light using different words to appeal to a new generation. Some of the most dangerous heresies centered on Jesus Christ: Arianism (which asserted that the Son of God was not truly divine but created), Docetism (which held that the humanity of Christ and His sufferings were not real), and Nestorianism (a variation of Arianism).