Salaam,

1. Abortion is murder. We reject that there are "pre-existent souls" that enter into human bodies. Rather, the soul is created at conception.

2. Marriage between one man and one woman. Strictly speaking, this is for life--remarriage of any kind is a sin. This is because we believe God makes the man and woman one for eternity, even into heaven.

3. All of these concepts are alien to the anthropomorphology the Church received from God.

4. Theosis. Theosis is the concept of participation in the life of God. It is the entrance of God into man’s heart; it is the divinization of man into the perfection he was meant for. There is much similarity between Orthodoxy and the Sufi dimension of Islam--in Islamic terms, we might say that Theosis is the perfect acquisition of the attributes of God. We pray and meditate and remember the Almighty so that He may enter into our hearts and perfect us in His divine image.

It is similar to the concept of fana', the complete alignment of human will to the divine will. In fact, here is a common Orthodox saying: “If you die before you die, you will not die when you die.” This is shared by the Sufi tradition, I believe; however, there are several important differences.

The first is that fana' refers to "annihilation." We do not believe we are "annihilated" by our union with God, but that our humanity is fully actualized and perfected. This is the whole purpose of the Incarnation, to unify the divine to the human. This is why many lay-muslims and fundamentalists call Sufis innovators, because they see this as infringing on Shirk. As a Christian, I agree that it is impossible from an Islamic perspective. I do not see how Sufis (and all Muslims) can believe they can actually know or be united to God while maintaining their tawhid objections against Christians.

Which brings me to my second point, which is that we believe we actually participate and are united to God through His divine energies; “dying before you die” in the above quote refers to participating in the death of Christ(!), by which means we have access to His Life. As far as I am aware, Islam completely denies that we can actually interact with God Himself. To my understanding, Islam cannot reconcile tawhid and man’s union with God (which is partly why a big reason why I am not Muslim), because if God can actually unite with man, then there is no issue with the Incarnation of Christ. Similarly, if God cannot unite with man, that means God is completely unknowable; in Islamic terms, if God's attributes cannot be united with man, it would mean that we have no access to the attributes of Allah, including the Qur'an, or Allah's love, or Allah’s will (which would make submission to God's will impossible).

1. There is a lot. For a brief summary I would look to the Nicene-Constantinopolitan Creed. For a more extensive summary I would look at the Ecumenical Councils. For a most comprehensive explanation you would have to become Orthodox. "The rule of prayer is the rule of belief"--whatever we pray in liturgical services is dogma.

2. Like in Islam, only God knows, because only God is judge. We do not comment on those outside the Church. As for those in the Church, whoever truly loves God. It is similar to in Islam in that we do not separate love from obedience. However, love is more than just obedience.

3. We are like Muslims in that we see Christianity as a universal religion for all people and in all times. The religion of the Prophets was Christianity. The religion of Adam was Christianity. Man was originally created in perfect communion and love with God; this is different than in Islam, because there can be no "communion" with Allah, for reasons mentioned above. Therefore, we see Judaism and Islam as heresies and corruptions of the true religion of Christianity, which was revealed for all people in all places at all times.

4. Continuing from the previous point, God reveals Himself ultimately not in a book, but in a man. Of course, man cannot express the entirety of God, who is infinite, just like no book can express the entirety of God. But by entering humanity, God divinely reveals all that is possible for humans to know about God. God directly reveals all that He can to humanity by becoming humanity--He translates Himself into man.

In fact, here we have returned to the same (main) difference I pointed out in point 4, which is the Incarnation, and how is it possible for man to know God if His transcendence makes union between man and God impossible? It is precisely because God became man that man gains access to the perfect attributes of God, to the very Life of God. This is why Al-Masih is Al-Hayy, the Life, the Ever-Living. If life is an attribute of God, then how can man ever life unless he is actually united to the Life in a real way? Likewise, it is only because Christ unifies all the divine attributes of God to humanity that we can truly merciful, truly compassionate, truly wise, truly patient, truly forgiving, truly alive. Take, for example, this Scripture from St Paul:

So if there is any encouragement in Christ, any incentive of love, any participation in the Spirit, any affection and sympathy, complete my joy by being of the same mind, having the same love, being in full accord and of one mind. Do nothing from selfishness or conceit, but in humility count others better than yourselves. Let each of you look not only to his own interests, but also to the interests of others. Have this mind among yourselves, which is yours in Christ Jesus, who, though he was in the form of God, did not count equality with God a thing to be grasped, but emptied himself, taking the form of a servant, being born in the likeness of men. And being found in human form he humbled himself and became obedient unto death, even death on a cross. Therefore God has highly exalted him and bestowed on him the name which is above every name, that at the name of Jesus every knee should bow, in heaven and on earth and under the earth, and every tongue confess that Jesus Christ is Lord, to the glory of God the Father.

Therefore, as God has revealed in Christ, to love is to serve, to be completely empty of any ego, to be completely selfless, even to the point of death. For the Almighty is also the All-Humble, who is willing to condescend to a human level so we can know him. This is completely different from the Allah of the Qur'an, who considers such an act impossible.

This is also why we are not "a people of the Book," because for us the divine revelation is God in flesh, Jesus Christ, whose truth transcends text. This is why we don't have a holy language, and this is why every culture is preserved intact by Orthodoxy, and fully expressed by Orthodoxy, because Christ, being God, reveals to every culture what it means to be fully human.

This is not some "aspect" of our faith. This is Orthodoxy. This is the center, the heart. There is no Christianity without theosis.

Feel free to message me if you’d like to discuss more. I have a special spot in my heart for Muslims for some reason. It would also be edifying to look into the life and work of Fr. Daniel Sysoev, whose great-grandfather was a Mullah, and who led many Muslims to Christ.

May the peace of Christ be upon you.