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Cyril Lucaris (or Lucar), the Patriarch of Alexandria and later of Constantinople, used this Greek term to express the idea for which the Latin term is transsubstantiatio (transubstantiation), which likewise literally means a change of substantia (substance, inner reality), using, in the 1629 Latin text of his The Eastern Confession of the Orthodox Faith, the term transsubstantiatio, and, in the Greek translation published in 1633, the term μετουσίωσις.
To counter the teaching of Lucaris, who denied transsubstantiatio/μετουσίωσις, Metropolitan Petro Mohyla of Kiev (also called Peter Mogila) drew up in Latin an Orthodox Confession, defending transubstantiation. Translated into Greek, using "μετουσίωσις" for the Latin term "transubstantiation", this Confession was approved by all the Greek-speaking Patriarchs (those of Constantinople, Alexandria, Antioch, and Jerusalem) in 1643, and again by the 1672 Synod of Jerusalem (also referred to as the Council of Bethlehem).
Theology and dogmatic status 
According to the Eastern Orthodox theology, "metousiosis" in Orthodox use should not be taken as a literal equivalent for the Catholic concept of transubstantion. Eastern theologians who use the word "transubstantiation" or "metousiosis" are careful to exclude the notion that it is an explanation of how the bread and wine of the sacrament are changed into the body and blood of Christ, instead of being a statement of what is changed. So, for an instance, "metousiosis" can be also used to describe the Eucharist in manner of St. Irenaeus or St. John Chrysostom, who taught about two natures present, both earthly (wine or bread itself) and heavenly (the Christ itself).
Reception in the West 
Since the Eastern Orthodox Church accepts as dogma only the solemn teaching of seven Ecumenical Councils, this approval, though part of what the 1911 Encyclopædia Britannica called "the most vital statement of faith made in the Greek Church during the past thousand years", was not equivalent to a dogmatic definition. However, the Protestant scholar Philip Schaff wrote in his Creeds of Christendom: "This Synod is the most important in the modern history of the Eastern Church, and may be compared to the Council of Trent. Both fixed the doctrinal status of the Churches they represent, and both condemned the evangelical doctrines of Protestantism ... the Romish doctrine of transubstantiation (μεταβολή, μετουσίωσις) is taught as strongly as words can make it."
The Roman Catholic apologetics website Orthodoxy and Transubstantiation gives, in English translation, a collection of several other instances, from as early as the 15th century, in which councils, individual ecclesiastics, and other writers and theologians of the Eastern Orthodox Church used the Greek term in the same sense as the Latin term.
The term metousiosis is, of course, not found in the text of the Eastern Orthodox Church's Divine Liturgy, just as the term transubstantiation is not found in the text of the Latin Eucharistic liturgy.
Original text of The Longer Catechism of the Orthodox, Catholic, Eastern Church, known also as The Catechism of St. Philaret, did not include the term metousiosis. It was added only in third edition: "In the exposition of the faith by the Eastern Patriarchs, it is said that the word transubstantiation is not to be taken to define the manner in which the bread and wine are changed into the Body and Blood of the Lord; for this none can understand but God; but only thus much is signified, that the bread truly, really, and substantially becomes the very true Body of the Lord, and the wine the very Blood of the Lord." The official Greek version of this passage (question 340) uses the word "metousiosis".
This declaration of the 1672 Orthodox Synod of Jerusalem is quoted by J.M. Neale (History of Eastern Church, Parker, Oxford and London, 1858) in a slightly different translation, as follows: "When we use the word metousiosis, we by no means think it explains the mode by which the bread and wine are converted into the Body and Blood of Christ, for this is altogether incomprehensible . . . but we mean that the bread and wine are changed into the Body and Blood of the Lord, not figuratively or symbolically, nor by any extraordinary grace attached to them . . . but . . . the bread becomes verily and indeed and essentially the very true Body of the Lord, and the wine the very Blood of the Lord."
An English translation of the full, quite lengthy, declaration by this Orthodox Council, called by Patriarch Dositheos of Jerusalem, can be found at the Web site Chapter VI of Acts and Decrees of the Synod of Jerusalem.
Writing in 1929, Metropolitan of Thyatira Germanos said that an obstacle to the request for union with the Eastern Orthodox Church presented in the seventeenth century by some Church of England bishops was that "the Patriarchs were adamant on the question of Transubstantiation", which, in view of the Thirty-Nine Articles, the Anglican bishops did not wish to accept.
See also 
- Orthodoxy and Transubstantiation/Metousiosis
- The Longer Catechism of the Orthodox, Catholic, Eastern Church, questions 338-340
- Проф. А. Осипов. Μεταβολή или transsubstantiatio?
- Николай Успенский. Святоотеческое учение о непостижимости природы евхаристии.
- Проф. А. Осипов. Μεταβολή или transsubstantiatio?
- Progress Towards the Re-Union of the Orthodox and Anglican Churches. By the Most Rev. Archbishop Germanos, Metropolitan of Thyatira. The Christian East, Spring, 1929, pp. 20-31