What was a major heresy addressed at the Council of Nicea?

The Council of Nicea, held in 325 AD, primarily addressed Arianism, which was a significant theological controversy at that time. Arianism, propagated by the priest Arius, challenged the understanding of the nature of Christ, asserting that Jesus Christ was a created being and thus not co-eternal with God the Father. This view contradicted the orthodox belief in the Trinity, which holds that the Father, Son, and Holy Spirit are three distinct persons but of one essence, fully divine and co-equal.

The council was summoned to resolve this dispute and to unify Christian doctrine. The outcome was the Nicene Creed, which clearly affirmed the divinity of Christ, stating that He is "begotten, not made, consubstantial with the Father." This established a foundational framework for Christian orthodoxy and countered the Arian position, making it a pivotal moment in early Church history in defining the nature of Christ and His relationship to God the Father.

In contrast, the other heresies listed—Pelagianism, Modalism, and Docetism—were addressed in later councils and periods. Pelagianism denied original sin and emphasized human free will, Modalism viewed the Father, Son, and Holy Spirit as different