If by "Orthodox Catholics" you are referring to Catholics who follow the teachings of the Church, then they believe what the Church teaches about it.
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from The Catechism of the Catholic Church, second edition, English translation 1994
The Final Purification, or Purgatory
1030 All who die in God's grace and friendship, but still imperfectly purified, are indeed assured of their eternal salvation; but after death they undergo purification, so as to achieve the holiness necessary to enter the joy of heaven.
1031 the church gives the name Purgatory to this final purification of the elect, which is entirely different from the punishment of the damned. (Cf. Council of Florence (1439): Denzinger 1304; Council of Trent (1563): Denzinger 1820; (1547): 1580; see also Benedict XII, Benedictus Deus (1336): Denzinger 1000) The Church formulated her doctrine of faith on Purgatory especially at the Councils of Florence and Trent. the tradition of the Church, by reference to certain texts of Scripture, speaks of cleansing fire: (Cf. 1 Cor 3:15; 1 Pet 1:7.)
As for certain lesser faults, we must believe that, before the Final Judgment, there is a purifying fire. He who is truth says that whoever utters blasphemy against the Holy Spirit will be pardoned neither in this age nor in the age to come. From this sentence we understand that certain offenses can be forgiven in this age, but certain others in the age to come. (St. Gregory the Great, Dial. 4, 29: J.P. Migne, ed., Patrologia Graeca {Paris, 1857-1866} 77, 396; cf. Mt 12:31.)
1032 This teaching is also based on the practice of prayer for the dead, already mentioned in Sacred Scripture: "Therefore [Juda Maccabeus] made atonement for the dead, that they might be delivered from their sin." (2 Macc 12:46.) From the beginning the Church has honored the memory of the dead and offered prayers in suffrage for them, above all the Eucharistic sacrifice, so that, thus purified, they may attain the beatific vision of god. (Cf. Council of Lyons II (1274): Denzinger 856) The Church also commends almsgiving, indulgences, and works of penance undertaken on behalf of the dead:
Let us help and commemorate them. If Job's sons were purified by their father's sacrifice, why would we doubt that our offerings for the dead bring them some consolation? Let us not hesitate to help those who have3 died and to offer our prayers for them. (St. John Chrysostom, Hom. in 1 Cor. 41, 5: J.P. Migne, ed., Patrologia Graeca {Paris, 1857-1866} 61, 361; cf. Job 1:5
If by "Orthodox Catholics, you are referring to the Eastern Orthodox Christians or the Greek Orthodox Christians, then you need to ask your question in their category.
Roman Catholics believe in the concept of purgatory, a place where souls are purified before entering heaven. They also believe in the doctrine of original sin, which states that all humans inherit sin from Adam and Eve. On the other hand, Orthodox Christians do not believe in purgatory and have a different understanding of original sin, viewing it more as a tendency towards sin rather than an inherited guilt.
Catholicism is the major religion that believes in the concept of purgatory, a place where souls are purified before entering heaven. Some branches of Eastern Orthodox Christianity also hold beliefs similar to purgatory.
Roman Catholics believe in Papal Primacy, Papal Infallibility, the Immaculate Conception, and Purgatory while Eastern Orthodox people do not. Roman Catholics believe that the Holy Spirit proceeds from the Father and the Son, while Eastern Orthodox people believe that the Holy Spirit only proceeds from the Father.
No, Lutherans do not believe in purgatory as a part of their faith.
No, Protestants do not believe in purgatory as part of their faith. Purgatory is a concept in Catholicism where souls are believed to undergo purification before entering heaven, but it is not a belief held by Protestants.
Yes, Purgatory was in the Book of Cannon which the protestant leaders removed from the bible any mention of purgatory. The Mormons also believe in 3 different levels of heaven which could be considered a purgatory.
Most Protestants believe in Heaven & Hell, but, no Purgatory.
No, but the Orthodox Church does believe in the Resurrection from the dead at the end of time.
Among groups who believe that the body will physically reside in purgatory, the soul is presumed to stay with the body. Many Christian sects believe that the soul suffers in purgatory, while the body remains interred (or whatever) until resurrection.
Whether or not purgatory existed.
Orthodox is a religion. They believe in the Bible, and in God. The difference is they are cool.
"Believe in" is not quite right. Purgatory as a place was never an official, promulgated teaching of the church. In 1999 Pope John Paul II declared that the term Purgatory does not indicate a place, but "a condition of existence". See link for everything you ever wanted to know (and then some) about Purgatory. The article discusses the positions of many other churches.