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This term corresponds to the celebrated homoou sios (μοούοιος, Latin consubstantialis ), with which the Council of nicaea i in 325 (H. Denzinger, Enchiridion symbolorum, ed. A. Schönmetzer (32d ed. Freiburg 1963) 125) designated the Son's full divinity and equality with the Father, and which the Council of chalcedon in 451 (Enchiridion symbolorum 301) used to designate the Son's possession of a true and perfect humanity essentially like ours. The Holy Spirit (e.g., Enchiridion symbolorum 853) and the entire Trinity (e.g., Enchiridion symbolorum 421, 554, 800, 805, 851) also receive this designation.

Historical Aspects: Trinitarian. Homoousios does not appear in Scripture, though both its Trinitarian and Christological senses are founded on what the New Testament says of the relationships of the Son with the Father (e.g., Jn 10.30; 14.910) and with other men (e.g., Gal4.4). The word, already used by Gnostics and Neoplatonists, was first employed in orthodox Christian circles by Clement and Origen; Origen is the first to apply it to the relationship of Son and Father (Frag. in ep. ad Hebr.; Patrologia Graeca, ed. J. P. Migne, 14:1308). It appears thereafter to have won considerable favor at Alexandria, for the anti-Sabellian bishop Dionysius is blamed for his refusal to use it; but his defense, in reply to a letter from his Roman namesake, makes it clear that he admits the conception but avoids the word because it is not found in Scripture (Athanasius, De sent. Dionysii 18; Patrologia Graeca 25:505). The synod of Antioch in 268 condemned its use in Paul of Samosata, possibly because he gave it a Monarchian sense; the matter is obscure.

At Nicaea I the Fathers, reluctant to have recourse to nonscriptural terms in condemning arianism, felt compelled to do so by the fact that the Arians could accept, in their own meaning, the more traditional formulations. Homoousios was the principal term inserted, along with "from the substance [ousia ] of the Father," to exclude their denial of the full divinity of the Son. The con-substantiality defined by Nicaea I, then, has an anti-Arian import and affirms essentially that the Son is equal to the Father, as divine as the Father, being from His substance and of the same substance with Him; it follows necessarily that the Son cannot belong to the created, as Arius maintained. At Nicaea I and later, opposition to homoousios arose on four counts (cf. Kelly, Creeds 23842): (1) that it conceived the divine substance as divisible, hence material; (2) that it was Sabellian; (3) that it had been condemned at the synod of Antioch in 268; and (4) that it was nonscriptural. Each of these charges was met successfully either at the Council or later, especially by Athanasius.

Nicaea I said nothing explicitly about the character of the divine unity implied in consubstantiality; this was not its problem. The issue of unity was raised in the post-Nicene polemics, with the final clarification, thanks to athanasius and the Cappadocians, that there is absolute (and not merely specific) identity in essence (ousia ), but distinction in hypostasis (note that Nicaea I had used ousia and hypostasis synonymously). The view once held by Harnack and others, therefore, contrasting a numerical identity in Nicaea I with a merely specific identity in the "Neo-Nicenes" (Cappadocians), has today generally lost favor; the faith of the Cappadocians in the perfect unity and simplicity of the Godhead (which transcends and excludes that numerical unity which is proper to material being) precludes such an interpretation. Another idea once in vogue is that Athanasius' heroic struggle after Nicaea I was primarily a defense of homoousios; in fact he uses it rarely in his anti-Arian works. It is notable that the first Council of Constantinople in 381 (Enchiridion symbolorum 150), in defining against the Macedonians the full divinity of the Holy Spirit, avoided the term homoousios, even though the doctrine of consubstantiality is implicit.

It must not be thought that consubstantiality was a conception peculiar to the Eastern Church. While it seems doubtful that Hosius of Cordoba introduced homoousios at Nicaea I as a direct result of the Western consubstantialis, the latter term, and still more consubstantivus, was used by Tertullian [Adv. Hermog. 44.3 (Corpus Christianorum. Series latina (Turnhout, Belg. 1953) 1:433); Adv. Valent. 12.5; 18.1; 37.2 (Corpus Christianorum. Series latina 2:764, 767, 778)], whose unius substantiae (Adv. Prax. 2.4; Corpus Christianorum. Series latina 2:1161) represented the leading Western formulation of consubstantiality. The Westerners at Nicaea I most likely welcomed homoousios as apt to express not only the perfect divinity of the Son but the unity of the Godhead, for which they had always been especially concerned. Eastern and Western affirmations of consubstantiality and of Trinitarian unity, while identical in the faith being professed, were different in derivation and formulation. In the Greek conception, the Father is the principle of unity, and Son and Spirit are consubstantial with Him because of generation and procession from Him. In the Latin conception, the divine substance itself is the principle of unity; all three Persons are consubstantial because all three possess equally the divine substance.

Historical Aspects: Christological. It was natural that homoousios, after its long Trinitarian career, should be employed also in Christology to indicate that Christ has the same nature as other men. It is found as early as Eustathius of Antioch (d. 337?; Theodoret, Eran. 1.56; Patrologia Graeca, 83:88). It was understandably favored by the Antiochene school. Theodoret of Cyr witnesses to the double consubstantiality of Christ, with the Father and with us (Interp. ep. 1 ad Cor. 11; Patrologia Graeca 82:312), and it was probably due to his influence that this language is found in the Formula of Union (H. Denzinger, Enchiridion symbolorum 272) on which John of Antioch and Cyril of Alexandria agreed in 433, and thence in the definition of Chalcedon. The formula is anti-Apollinarian and anti-Eutychean in intent. It counteracts the position of some Apollinarists that the flesh of the Incarnate Son is consubstantial with divinity. Along with "two natures after the Incarnation," it was a touchstone of orthodoxy in the trial of Eutyches under Flavian in 448 (Acta conciliorum oecumenicorum (Berlin 1914) 2.1.1:14245). Eutyches reluctantly accepted the formula, but evasively, and when pressed on the question of two natures was eventually condemned. The definition of Chalcedon enshrined the double consubstantiality of Christ in the Church's official teaching.

Doctrinal Content. Consubstantiality says identity of substance (nature, essence) between really distinct equals. The three Divine Persons, really distinct from one another, possess equally the one divine substance, or essence, i.e., divinity. Because of the absolute unicity, unity, and simplicity of God, the identity of the substance is not merely specific but absolute, or numerical (provided the latter term be taken analogously). The consubstantiality of Christ according to His humanity with other men, on the contrary, affirms a specific, not numerical, identity of substance, or nature, between Christ and other men. The Chalcedonian assertion of the double consubstantiality of Christ, with the Father according to His divinity, with us according to His humanity, is a more precise way of saying that Christ is true and perfect God, and true and perfect man. In other words, it is, in the context of the Arian and Apollinarist-Eutychean deviations, a dogmatic reaffirmation of the mystery of the Incarnation.

Significance. Implicit in this formulation in terms of consubstantiality of the two basic mysteries of Christianity is a threefold assertion of primary theological and religious significance. (1) It is legitimate and necessary, for the understanding and defense of the Christian faith, to move from the (generally) functional and dynamic conceptions of Scripture to the ontological conceptions typical of Christian dogma. (2) The employment of categories taken from Greek philosophy in the Church's dogmatic pronouncements has represented not a Hellenization of Christianity but a Christianization of Hellenism.(3) A real and not merely verbal doctrinal development is an exigency of the Christian revelation, which has been made to men, who as finite spirits may and must pursue progressive understanding even of divine mysteries, and as incarnate spirits must pursue it under the conditions of human history. Nicaea I and Chalcedon, and the subsequent endorsements of Christian tradition have asserted this legitimacy and exigency as regards the fact; the further penetration and theoretical justification of the fact are a continuing task for historical and theological understanding.

See Also: generation of the word; incarnation; jesus christ; logos; nature; person (in theology); person, divine; processions, trinitarian; theology, influence of greek philosophy on; trinity, holy; word, the.

Bibliography: j. n. d. kelly, Early Christian Creeds (2d ed. New York 1960) 24262; Early Christian Doctrines (2d ed. New York 1960) 22379. h. quilliet, Dictionnaire de théologie catholique, ed. a. vacant et al., 15 v. (Paris 190350) 3.2:160415. j. c. murray, The Problem of God Yesterday and Today (St. Thomas More Lectures 1; New Haven 1964) 3160. g.l. prestige, God in Patristic Thought (Society for Promoting Christian Knowledge 1935; repr. 1959) 197281. v. c. de clercq, Ossius of Cordova: A Contribution to the History of the Constantinian Period (Washington 1954) 21889. i. ortiz de urbina, El símbolo niceno (Madrid 1947) 178216. b. lonergan, De Deo trino, 2 v. (v.1 2d ed., v.2 3d ed. Rome 1964) 1:7587, 11354. r.v. sellers, The Council of Chalcedon (London 1953) 6469, 21213. l. bouyer, "Omoousios: Sa signification historique dans le symbole de foi," Les Sciences philosophiques et théologiques 1 (194142) 5262.

[t. e. clarke]

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