Heresy of the Week

Arianism (4th Century)

One of the greatest heresies the Church has ever fought was Arianism. Arius taught that Christ was less than divine, that he was a creature made by God. By disguising his heresy using orthodox or near-orthodox terminology, he was able to sow great confusion in the Church. He was able to muster the support of many bishops, while others excommunicated him.

Arianism was solemnly condemned in 325 at the First Council of Nicaea, which defined the divinity of Christ, and in 381 at the First Council of Constantinople, which defined the divinity of the Holy Spirit. These two councils gave us the Nicene creed, which Catholics recite at Mass every Sunday.

From Catholic Answers.