Arianism is a Christian "heresy" that was first proposed early in the 4th century by the Alexandrian presbyter Arius. It affirms that Christ is not a truly divine being (because uncreated, self-existing, and eternal), but a created being. Arius' based this formulation on his belief in the uniqueness of God, who is alone self-existent and immutable; the Son is not self-existent, and therefore cannot be God. Because the Godhead is unique, it cannot be shared or communicated, so the Son cannot be God. Because the Godhead is immutable, the Son, who is mutable (described in the Gospels as subject to growth and change), cannot be God. The Son must, therefore, be accounted a creature who has been called into existence out of nothing and has had a beginning. Arianism flies directly in the face of othodox Trinitarianism.