The Holy Trinity and Arianism

"The movement for denying the full Godhead of Christ and making Him a creature took its title from one Areios (in the Latin form Arius), a Greek-speaking African cleric rather older than Constantine, and already famous as a religious force some years before Constantine's victories and first imperial power....In all their various forms and under all their technical names (Monophysites, Monothelites, Nestorians, the names of the principal three—and there were any number of others) these movements throughout the Eastern or Greek half of the Empire were efforts at escaping from, or rationalizing, the full mystery of the Incarnation" (Hillaire Belloc, The Great Heresies, 1936, pp. 28 - 35)

"Arius taught that Christ 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" (Catholic Answers, The Great Heresies, 2018).