CONSOSTANZIALE. — This is the translation of the Greek term ὁμοούσιος (= of the same essence), which became Arianism (v.) at the time of the Council of Nicaea (325) and was inserted into the Creed of that council in order to express the substantial or essential identity of the Son with the Father (ὁμοούσιος τῷ Πατρὶ) and thus condemn the Arian error, which maintained a diversity of substance or essence (ἐκ ἐτέρας ὑποστάσεως ἢ οὐσίας) between the first two Persons of the Trinity.
But the term ὁμοούσιος, which is found for the first time in the Gnostic literature of the second century and then passed in the third century into Catholic vocabulary, has a history which, because of its various developments, has in recent times given rise to a controversy between Catholics and non-Catholics concerning the interpretation of the Nicene definition. The Lutheran Th. Zahn, followed by the liberal Protestants Harnack, Loofs, Seeberg, Gwatkin, and finally the false Coulange (Turmel, a priest condemned by the Church), maintained that the term, already rejected at the Synod of Antioch (269), which condemned Paul of Samosata, was adopted by the Council of Nicaea in the sense of numerical unity, whereas later, especially by the Cappadocian Fathers, it was interpreted in the sense of purely specific unity.
First of all, it should be noted that the concept of essential or substantial unity between the Father and the Son is already found in the Gospel, where Christ says: “I and the Father are one” (Jo. 10:30). The term ὁμοούσιος, used in this sense,
is already found in Origen (In Mt.: PG, 17, 309 A) and was known in Rome under Pope Dionysius (259–68). But since at that time the distinction between οὐσία and ὑπόστασις was not yet clear, the term ὁμοούσιος was open to misunderstanding, because it could signify identity of essence or of person. The Antiochene Synod of 269 condemned ὁμοούσιος because Paul of Samosata interpreted it in the sense of personal modalism (v.). So attests Hilary (De Synodis, 81: PL, 10, 534).
At the Council of Nicaea, the term ὁμοούσιος retained its antecedent meaning, also confirmed by the Cappadocian Fathers: it formally indicated neither numerical unity nor purely specific unity. It intended to affirm that the substance of the Word did not belong to the category of creatures but to the same category as that of the Father. Virtually, however, the unity called numerical was also affirmed, because at the beginning of the same Nicene Creed it had been defined that there is “one God the Father.” After the Council, however, the Arians attacked ὁμοούσιος as a modalist expression proper to Sabellianism (v.), which removed every distinction of person in the Trinity. For this reason the Fathers (Athanasius, Basil) did not insist further on the term, but continued to defend the concept of consubstantiality, even making a favorable concession to the formula of the Homoiousians (v.), in which not identity but substantial likeness was asserted. Nevertheless, these Fathers understood and explained this likeness in an absolute sense, which was equivalent to identity. In short, they unified the use of the technical term without compromising its doctrinal meaning, already defined at Nicaea.
Subsequently, once the distinction between οὐσία and ὑπόστασις had been clarified, the Latin formula una natura in tribus personis also spread in the East, dispelling every ambiguity: μία οὐσία, τρεῖς ὑποστάσεις.
There is therefore no point in speaking of Neo-Nicene doctrine. At the Council of Constantinople (381), ὁμοούσιος was also asserted with regard to the Holy Spirit against the Macedonians.