homoousios

[hoe-moe-oo’-see-oss]

(Greek homo-, ”same” + Greek ousia, “substance” = “of the same substance” “consubstantial”)

This is the Trinitarian term that expresses a belief that Christ is of the same substance or nature as the Father. This word was central to the fourth-century debate between Athanasius and the Arians. Arius believed that Christ was of “similar substance” to the Father (homoiousios), but not of the “same substance” (homoousios). The two positions were separated by one letter in Greek, an iota. Thus the common phrase “it doesn’t make one iota of difference.” The Council of Nicea (325) believed that Christ shared in the exact same essence as the Father and therefore adopted the term homoousios to describe the relationship between the members of the Godhead. This concept was further developed by the Cappadocian fathers and further applied to all three members of the Trinity at the Council of Constantinople (381).