A list of the main doctrinal differences between the Orthodox Church and the Roman Catholic are given in a piece cautioning against unwise one-world ecumenism:
1. The Eastern Orthodox reject the Roman Catholic notion of purgatory (Ware, T. The Orthodox Church. Penguin Books, London, 1997, p.p. 255 and Aghiorgoussis, Maximos. The Dogmatic Tradition of the Orthodox Church. Copyright: © 1990-1996. http://www.goarch.org/en/ourfaith/articles/article8038.asp 08/18/07).
2. The Eastern Orthodox number the ten commandments as they originally were (Mastrantonis, G. The Ten Commandments. Copyright: © 1990-1996 Greek Orthodox Archdiocese of America. http://www.goarch.org/en/ourfaith/articles/article7115.asp 05/14/07) and not as the Roman Catholics number them. Those of Rome combine the first two, even though that is not what those such as Clement of Alexander (2nd century) did (Clement of Alexandria. Stromata, Book VI).
3. The Eastern Orthodox believe in baptism by immersion (Ware, p. 278). The Roman Catholics usually employ sprinkling.
4. Most of the Eastern Orthodox (presuming no abortive devices are used), as do most others, believe in “the responsible use of contraception within marriage” (Ware, p.296 and Harakis S. The Stand of the Orthodox Church on Controversial Issues. http://www.goarch.org/en/ourfaith/articles/article7101.asp 8/20/05). The Roman Catholic position seems to be much more limited.
5. The Eastern Orthodox reject “the dogma of the immaculate conception of the Virgin” (Clendenin D.B. ed. Eastern Orthodox Theology, 2nd ed. Baker Academic, 2003, p.67). That is a Roman Catholic dogma (Ott L. Fundamentals of Catholic Dogma. Translated into English by James Bastible. Nihil Obstat: Jeremiah J. O’Sullivan. Imprimatur + Cornelius, 7 October 1954. Reprint TAN Books, Rockford (IL), 1974, pp. 199-202).
6. The Eastern Orthodox teach that presbyters (which they call “priests,” but we in the Church of God) tend to call “ministers” or “elders”) can be married (Damaskinos Papandreou, Orthodox Metropolitan of Switzerland. The Orthodox Churches and Priestly Celibacy. http://www.orthodoxresearchinstitute.org/articles/misc/damaskinos_celibacy.htm viewed 02/04/08). The Roman Church requires celibacy for all presbyters, even though that was not its original position (Fortesque A. Transcribed by Marie Jutras. Eastern Monasticism. The Catholic Encyclopedia, Volume X. Copyright © 1911 by Robert Appleton Company. Online Edition Copyright © 2003 by K. Knight. Nihil Obstat, October 1, 1911. Remy Lafort, S.T.D., Censor. Imprimatur. +John Cardinal Farley, Archbishop of New York).
7. The Eastern Orthodox, similar to the Church of God, teach that, “Christians must always be ‘People of the Book’ “ (Ware, p.199). Yet, throughout history, the Church of Rome has tended to place more emphasis on the Living Magisterium and non-biblical sources for much of its doctrines.
8. The Eastern Orthodox do not observe Ash Wednesday. The Church of Rome admits that it added this observance in the Middle Ages (Thurston, Herbert. “Ash Wednesday.” The Catholic Encyclopedia. Vol. 1. Nihil Obstat. March 1, 1907. Remy Lafort, S.T.D., Censor. Imprimatur. +John Cardinal Farley, Archbishop of New York. New York: Robert Appleton Company, 1907. 4 May 2009 ).
9. The Orthodox do not believe in the concept of “papal infallibility.” That concept became a dogma for the Church of Rome in the 19th century (at Vatican I) (McBrien, Richard P. Lives of the Popes: The Pontiffs from St. Peter to Benedict XVI. Harper, San Francisco, 2005 updated ed., pp. 20-22).
10. Many (though not all) of the Eastern Orthodox, like the Church of God, believe that God has a plan of salvation that can occur at the time of the final judgment. (Ware, p.255). The Roman Church rejects the idea that salvation can be available after the first death and this has been clearly stated by Pope Benedict (Catechism of the Catholic Church, 1021. Imprimi Potest + Joseph Cardinal Ratzinger. Doubleday, New York, 1994, p. 153).
11. The Roman Catholic view of eternal torment is rejected by the The Eastern Orthodox (Ware, p. 262).
12. Neither the Orthodox nor Protestants believe that the jurisdiction of Rome has any real bearing on apostolic succession.
It perhaps should be pointed out that the Orthodox, who generally make less pronouncements than the Vatican tends to, condemned the papacy as a major heresy in 1848:
” 2. Hence have arisen manifold and monstrous heresies which the Catholic Church, even from her infancy, has been forced to combat with the panoply of God, and ‘ the sword of the Spirit, which is the Word of God,’ and has triumphed over all unto this day, and will triumph to the end, ever shining forth brighter and stronger after the struggle.
” 3. Of these heresies some have altogether perished, some are in their decline, but others nourish more or less, until the time of their overthrow, when, being struck with the lightning of the anathema of of the seven (Ecumenical Synods, they become extinct, even though they last for a thousand years; for the orthodoxy of the Catholic Apostolic Church, as inspired by the living Word of God, alone endures for ever, according to the infallible promise of our Lord…—Matt, xviii. 18.
” 4. Of these heresies widely-diffused was formerly Arianism, and now is the Papacy, which, though still flourishing, shall, like the former, pass away and be cast down, and a great voice from Heaven shall cry, ‘ It is cast down.’—Rev. xii. 10…
” 10. Every one of our brethren and children in Christ clearly perceives that the words of the present Bishop of Rome, like those of his anti-synodical predecessors, are not words of peace and compassion, as he says, but of deceit and quibbling, tending to self-aggrandisement; but the orthodox will not be beguiled therewith, for the Word of the Lord is sure—’ A stranger will they not follow, but will flee from him, for they know not the voice of strangers.’
(Encyclical Letter of the Eastern Orthodox, 1848. As cited in The Benares magazine, No. 31, 1851. W.H. Haycock, 1851. Original from Oxford University Digitized, Nov 24, 2006, pp. 370-371,373)
Perhaps it should be mentioned that “Rev. xii. 10” teaches about the “accuser of the brethren” (a reference to Satan in verse 9) being cast down. Thus the Orthodox officially seem to have condemned the papacy as Satan the devil.
Not only does the Orthodox Church consider the institution of the Papacy and the doctrine of Papal infallibility heretical, it considers many – not all – of the instances of stigmata and visions exhibited by Catholic saints to be evidence not of sanctity but of delusion and vainglory, especially when they are sought out deliberately.
Although I wouldn’t go so far as to call such displays Satanic, I agree that more than a few are the results of a misguided effort of will, very similar to the efforts of some yogis and ascetics in Hinduism and similarly lacking in moral content, while sometimes providing grave opportunities for moral depravity.
Asceticism (what is called tapas in India) and mental focus can lead to psychosomatic symptoms (markings on the skin, sensations) as well as psychic abilities – siddhis -(levitation, bilocation) of all kinds, but whether this is always a saintly thing, or even good, is the question.
In many cases (not all), the Orthodox answer, “no,” is the correct one.
The heart, as the Bible points out, is endlessly self-deceiving.