After the church had agreed that Jesus Christ is fully God, they continued to struggle with how his humanity and deity could coexist.  Some views such as Arianism and Apollinarianism denied either Christ’s full deity or his full humanity, while other views such as Nestorianism and Eutycianism affirm both natures, but stand at opposite extremes of how they relate.

Eutycianism is also known as monophysitism (monos, “single,” physis, “nature”).  It assumes that Christ can have only one nature, which is a mixture of divine nature and human natures, such that the human becomes divine and the divine human. This confuses both Christ’s true humanity and his true deity.  The view was officially considered heresy by the Council of Chalcedon in 451 CE.