The union in one person, or hypostasis, of the divine and human natures. Jesus Christ is both God and man in virtue of the hypostatic union, a mystery of faith in the strict sense. "As God he was begotten of the substance of the Father before time; as man he was born in time of the substance of his mother. He is perfect God; and he is perfect man, with a rational soul and human flesh. He is equal to the Father in His divinity but He is inferior to the Father in his humanity. Although he is God and man, he is not two but one Christ. And he is one, not because his divinity was changed into flesh, but because His humanity was assumed to God. He is one, not at all because of a mingling of substances, but because he is one person" [the so-called Athanasian Creed; H. Denzinger, Enchiridion symbolorum 76; tr. J. F. Clarkson et al., The Church Teaches (St. Louis 1955) 5–6].
Biblical affirmations of the divinity and humanity of Christ were transformed into technical, theological expressions and (to some extent) explanations of the mystery when heresies began to pervert the true faith. Docetism, Arianism, and Apollinarianism attacked the true humanity of Christ; Arianism, rationalism, Modernism, the true divinity. In addition, nestorianism, adop tionism, monophysitism, and monothelitism erroneously understood the manner of the union between the divine and human natures. The evolution of the fixed technical terminology of the hypostatic union was gradual. The Council of chalcedon (451) established the usage whereby hypostasis means person and whereby ousia and physis mean substance and nature. A consideration of the Council of Nicaea I's use of hypostasis and ousia (Denzinger 126) will bring out the earlier (325) fluidity of terminology.
See Also: jesus christ, ii (in theology); hypostatic union, grace of; person (in philosophy); person (in theology); nature; jesus christ, articles on.
Bibliography: a. michel, Dictionnaire de théologie catholique, ed. a. vacant et al. (Paris 1903–50) 7.1:437–568. m. schmaus, Lexikon für Theologie und Kirche, ed. j. hofer and k. rahner (Freiburg 1957–65) 5:579–583.
[e. a. weis]