Homoousion

Homoousion (ὁμοούσιον, from ὁμός, homós, same and οὐσία, ousía, being or essence) is a Christian theological term, most notably used in the Nicene Creed for describing Jesus (God the Son) as "same in being" or "same in essence" with God the Father (ὁμοούσιον τῷ Πατρί).

The same term was later also applied to the Holy Spirit in order to designate him as being "same in essence" with the Father and the Son. Those notions became cornerstones of theology in Nicene Christianity, and also represent one of the most important theological concepts within the Trinitarian doctrinal understanding of God.

Terminology
The term ὁμοούσιον, the accusative case form of ὁμοούσιος (homoousios, consubstantial), was adopted at the First Council of Nicaea (325) in order to clarify the ontology of Christ. From its Greek original, the term was translated into other languages. In Latin, which is lacking a present participle of the verb 'to be', two main corresponding variants occurred. Since the Aristotelian term ousia was commonly translated in Latin as essentia (essence) or substantia (substance), the Greek term homoousios was consequently translated into Latin as coessentialis or consubstantialis, hence the English terms coessential and consubstantial. Some modern scholars say that homoousios is properly translated as coessential, while consubstantial has a much wider spectrum of meanings. The Book of Common Prayer renders the term as "being of one substance with the Father."

From ὁμοούσιος (coessential), the theological term ὁμοουσιότης (coessentiality) was also derived. It was used by Greek-speaking authors, like Didymus of Alexandria and other theologians.

Pre-Nicene usage
The Bible mentions a few sayings of Jesus that suggest he claimed to be of a similar nature to God the Father. However, the theological language that would later develop was not used in the gospels.

The term ὁμοούσιος had been used before its adoption by the First Council of Nicaea. The Gnostics were the first to use the word ὁμοούσιος, while before the Gnostics there is no trace at all of its existence. The early church theologians were probably made aware of this concept, and thus of the doctrine of emanation, taught by the Gnostics. In Gnostic texts, the word ὁμοούσιος is used with the following meanings: For example, Basilides, the first known Gnostic thinker to use ὁμοούσιος in the first half of the 2nd century AD, speaks of a threefold sonship consubstantial with the god who is not. The Valentinian Gnostic Ptolemy says in his letter to Flora that it is the nature of the good God to beget and bring forth only beings similar to, and consubstantial with, himself. The term ὁμοούσιος was already in current use by the 2nd-century Gnostics, and through their works it became known to the orthodox heresiologists, though this Gnostic use of the term had no reference to the specific relationship between Father and Son, as is the case in the Nicene Creed.
 * Identity of substance between generator and generated.
 * Identity of substance between things generated of the same substance.
 * Identity of substance between the partners of a syzygy.

Tertullian (155–220), writing in Latin, nowhere uses any term corresponding exactly to the Greek word homoousios. However, in his theology, Father and Son are a single substance and a single hypostasis. That implies not only homoousios (same substance) but, more specifically, 'one substance'.

Sabellius did indeed use the term and he used it to say that Father and Son are a single hypostasis. In other words, he used the term not only to mean 'same substance' but, specifically, 'one substance.

Origen did not use the term. In opposition to Tertullian and Sabellius, he believed that Father, Son, and Spirit are three hypostases, meaning three distinct substances.

Around the year 260, the bishops of Rome and Alexandria; both named Dionysius, disagreed about the term. Some Sabellians in Libya as well as Dionysius of Rome believed in one hypostasis and used homoousios to say that. In contrast, Dionysius of Alexandria believed in three hypostases and, initially, denied the term. He later accepted it but only after the bishop of Rome applied pressure on him and only in a general sense of meaning 'the same type of substance'.

More or less at the same time, Paul of Samosata used the term to say that Father and Son are a single substance, a single hypostasis or Person. But, in the year 268, a council at Antioch condemned both Paul and the term homoousios.

In conclusion, before Nicaea, homoousios was preferred only by Sabellians, including Sabellius himself, the Libyan Sabellians, Dionysius of Rome, and Paul of Samosata. For them, Father and Son are a single Person with a single mind."'The word homousios had not had … a very happy history. It was probably rejected by the Council of Antioch, and was suspected of being open to a Sabellian meaning. It was accepted by the heretic Paul of Samosata and this rendered it very offensive to many in the Asiatic Churches.' (Philip Schaff)"The only non-Sabellian who accepted the term was Dionysius of Alexandria, but he accepted it reluctantly and only as meaning that the Father and Son are two distinct substances of the same type."'We can detect no Greek-speaking writer before Nicaea who unreservedly supports as applied to the Son.' (Hanson, p. 169)"

Adoption in the Nicene Creed
The Nicene Creed is the official doctrine of most Christian churches—the Catholic Church, Eastern Orthodox Church, Oriental Orthodox Churches, Church of the East, Lutheran Churches, Moravian Church, Anglican Communion, and Reformed Churches as well as other mainline Protestant and evangelical churches with regard to the ontological status of the three persons or hypostases of the Trinity: Father, Son, and Holy Spirit.

Origen seems to have been the first ecclesiastical writer to use the word homoousios in a nontrinitarian context, and it is evident in his writings that he considered the Son's divinity equal to the Father's, though he calls the Son "a creature", for man is but one of God's creatures. It was more clearly articulated by Athanasius of Alexandria and the Nicene Council that the Son was taken to have exactly the same essence with the Father, and in the Nicene Creed the Son was declared to be as immutable as his Father.

While it is common to find statements by their critics that Origen and other early apologist Church fathers held subordinationist views, Ilaria Ramelli discussed the "anti-subordinationism" of Origen.

Both the Nicene and Athanasian creeds affirm the Son as both begotten of, and equal to his Father. If so, many concepts of the Holy Trinity would appear to have already existed relatively early while the specific language used to affirm the doctrine continued to develop.

Some theologians preferred the use of the term ὁμοιούσιος (homoioúsios or alternative uncontracted form ὁμοιοούσιος homoiοoúsios; from ὅμοιος, hómoios, similar, rather than ὁμός, homós, same, common) in order to emphasize distinctions among the three persons in the Godhead, but the term homoousion became a consistent mark of Nicene orthodoxy in both East and West. According to this doctrine, Jesus Christ is the physical manifestation of Logos (or the Word), and consequently possesses all of the inherent, ineffable perfections which religion and philosophy attribute to the Supreme Being. In the language that became universally accepted after the First Council of Constantinople in AD 381, three distinct and infinite hypostases, or divine persons, the Father, the Son, and the Holy Spirit, fully possess the very same divine ousia.

This doctrine was formulated in the 4th century, during the Arian controversy over Christology between Arius and Athanasius. The several distinct branches of Arianism which sometimes conflicted with each other as well as with the pro-Nicene homoousian creed can be roughly broken down into the following classifications:
 * Homoiousianism (from ὅμοιος, hómoos, similar, as opposed to ὁμός, homós, same, common), which maintained that the Son was "like in substance" but not necessarily to be identified with the essence of the Father.
 * Homoeanism (also from ὅμοιος), which declared that the Son was similar to God the Father, without reference to substance or essence. Some supporters of Homoean formulae also supported one of the other descriptions. Other Homoeans declared that the father was so incomparable and ineffably transcendent that even the ideas of likeness, similarity or identity in substance or essence with the subordinate Son and Holy Spirit were heretical and not justified by the Gospels. They held that the Father was the Son in some sense but that even to speak of ousia was impertinent speculation.
 * Heteroousianism (including Anomoeanism), which held that God the Father and the Son were different in substance and/or attributes.

All of these positions and the almost innumerable variations on them which developed in the 4th century were strongly and tenaciously opposed by Athanasius and other pro-Nicenes, who insisted on the doctrine of homoousion or consubstantiality, eventually prevailing in the struggle to define this as a dogma of the still-united Western and Eastern churches for the next two millennia when its use was confirmed by the First Council of Constantinople (381). The struggle over the understanding of Christ's divinity was not solely a matter for the Church. The Roman Emperor Theodosius had published an edict, prior to the Council of Constantinople, declaring that the Nicene Creed was the legitimate doctrine and that those opposed to it were heretics.

It has also been said that the term homoousios, which Athanasius favored and which was ratified in the Nicene Council and Creed, was actually a term reported to also be used and favored by the Sabellians in their Christology. It was a term with which many followers of Athanasius were actually uncomfortable. The so-called Semi-Arians in particular objected to it. Their objection to this term was that it was considered to be "un-Scriptural, suspicious, and of a Sabellian tendency." This was because Sabellius also considered the Father and the Son to be "one substance", meaning that, to Sabellius, the Father and the Son were "one essential Person", though operating in different faces, roles, or modes. This notion, however, was also rejected at the Council of Nicaea, in favor of the Nicene Creed, which holds the Father and Son to be distinct yet also coequal, coeternal, and consubstantial divine persons.

The use of the word homoousios in the Nicene Creed was proposed by Emperor Constantine I, who convened and chaired the First Council of Nicea. By persuasion and by threats of excommunication and exile, Constantine obtained the endorsement of all but two of the attending bishops for the inclusion of the word.

After Nicaea
The view that homoousios was of fundamental importance is deeply mistaken. For about 25 years after Nicaea, nobody mentioned the term."'What is conventionally regarded as the key-word in the Creed, falls completely out of the controversy very shortly after the Council of Nicaea and is not heard of for over twenty years.'"Not even those who defended the term at Nicaea, nor Athanasius, the main defender of the term, nor the Western church, which is often described as the stalwart defender of Nicaea throughout the fourth century, mentioned the term during those decades.

Athanasius re-introduced the term into the debate in the 350s, some 30 years after Nicaea, but it took some time before the Western church adopted it. Since homoousios was first defended in the 350s, we see attacks on it only in the 350s.

This absence of the term homoousios in the 20 or more years after Nicaea means that it was not regarded as important. The term was a problem even for anti-Arians.

The term homoousion appears in the Nicene Creed not because it was an important concept, but merely to force Arius and his supporters to reject the Creed so that the emperor could exile them.

After Athanasius was exiled for violence in 335, he developed his polemical strategy in which he claimed that he was exiled for his opposition to Arianism. At first, his strategy did not include the term homoousios. But after Constantius became emperor of the entire empire in the early 350s, and after he attempted to isolate Athanasius, Athanasius added homoousios to his polemics.