The doctrine denying the true divinity of Christ, named after the Alexandrian priest Arius (c.250–c.336). It maintained that the Son was not eternal, or of one nature with God, but was a dependent instrument created for the redemption of the world. In 325 the General Council of Nicaea under Athanasius (296–373) defined and affirmed the doctrine of the coeternity and coequality of God and the Son. This doctrine of homoousion requires some confidence that we know, for example, how to count whether things are of one or two substances.