Gnosticism-
They believed that "matter was evil." This contradicts many Catholic teachings. It contradicts in Genesis when "god saw everything he had made, and it was good." It also contradicts the incarnation of Jesus; if Jesus was God he could not be made up of evil.

Arianism-
They taught that Jesus wasn't the Son of God, but a creature made by God. It caused a great confusion in the church when they were able to persuade bishops to follow them. Other people excommunicated them.

The Different Sects of the Church

Nestorianism-
This heresy was started by Nestorius, a bishop of Constantinople. He said that Mary did not deserve the title of "Mother of God" because she only held the human form of Jesus in her womb.