Translated from the Greek original by
Proptopresbyter George Dion. Dragas PhD, DD, DTh
1. Did God create, apart from the creation of the sensible cosmos and the creation of man, any other rational beings?
Yes. He did. God created another super sensible and spiritual world, and other intelligent beings, reason-endowed and self-determined.
2. Whence do we know about the super sensible cosmos?
We know from the Scriptures of the Old and the New Testament of the existence of the Angels.
3. Where does the Old Testament refer to the existence of Angels?
a) The first reference occurs in Gen. 16:78, etc., where it relates, that an Angel appeared to Hagar, but thenceforth Angels are mentioned in several chapters of the book of Genesis.
b) Then, there are references to Angels in the book of Deuteronomy, where Moses states, that “when the Most High separated nations as he dispersed the sons of Adam, He placed boundaries for nations according to the numbers of the Angels of God” (Deut. 32:8-9).
c) Likewise, Angels are mentioned in all the books of the Holy Scripture and in the book of Job, where we read: “Behold the Angels of the Lord came to stand before the Lord; and the devil came with them” (Job 1:6). There too we read, that “when stars were made, all my Angels praised me with a loud voice” (Job 38:7, cf. 40:14). Similar references are also in the book of the Kings, of Numbers, etc. 
4. Where does the New Testament refer to the creation of the super sensible cosmos?
There are many places in the New Testament which refer to angels, or good spirits, as well as evil angels, i.e. devils and evil spirits. In regard to the creation of angels the Apostle Paul relates the following: that “in Him [the Son of God] all things were created, things in heaven and things on earth, whether visible and invisible, whether thrones, or dominions, whether principalities or authorities; all things were made for Him and to Him” (Col. 1:16).
5. Why are angels called spirits?
They called so because of the spiritual nature and because they are immaterial and incorporeal.
6. Where in Holy Scripture do we read about the incorporeal nature of the angels?
Luke the Evangelist relates the following: “Touch me and see that spirit does not have flesh and bones as you see me having” (24:39). Also the Apostle Paul, admonishing the Ephesians to put on the whole armor of God so that they might withstanding the skimming of the devil, says: “that the fight is not against blood and flesh, but against the principalities and authorities, the cosmic rulers of the darkness of the present age, the spiritual beings of evil in the heavenly places” (Eph. 6:12-13).
7. What do the Fathers of the Church say about the spiritual nature of the angels?
The Fathers of the Church say that the angels do not participate in the solid earthly mater. This opinion of the Fathers was also formulated at the Seventh Ecumenical Council at Nicaea in the following way: “These precious and sacred icons, as it was already said, we honor and kiss and venerate as a matter of attributing honor … to the holy and incorporeal angels” (See the relevant Canon). St. Basil attributes to angels a body that is ethereal and fiery; In chapter 16 of his treatise On the Holy Spirit he says: “For the angels have a very fine body, but not totally incorporeal, as God is; hence they are in a place, and they become visible to those who are worthy according to the species of their own bodies.” St. Gregory the Theologian and John of Damascus regard the angels as incorporeal beings in relation to humanity: “an angel is called immaterial in contrast to us; for whatever is compared to God who alone is incomparable, is found to be solid and material; for indeed, only the divine being is immaterial and incorporeal”.  The divine Hilary says that every created being is by necessity corporeal. Origen too, took the Angels as having ethereal bodies  and so did many other Fathers. 
Holy liturgy in the Ss. Archangels' Orthodox Church, Maputo, Mozambique (from here). About Orthodox Church in Mozambique, see here.
8. Were the Angels liable to sin?
Yes indeed; because every rational and morally free creation that freely chooses the good is liable to sin; consequently, the angels too. John Damascenos says: “there is also a nature [that of the angels] which is rational, mindful and freely-determined, changeable with respect to choice, i.e. free to change; for everything created is also changeable”. 
9. What does Scripture say about this?
Holy Scripture says that some of the angelic orders fell into sin. The Apostle Jude says: “and the angels that did not keep their own rule, but left their proper dwelling, have been kept by Him in a dark place with eternal chains to be judged on the great day” (Jude verse 6). Also, our Lord Jesus Christ says: that “He saw Satan  falling from heaven like a lightening” (Luke 4:18).
10. How are the angels called who did keep their own rule?
They are called good spirits, in contrast to those that did not do so and are called devils.
11. Are the good angels liable anymore to fall into sin?
No; because their persistence in love for God and communion, and their free proclivity and choice have become, as it were, a natural and moral necessity, and so they do not decide for anything else but for the good, which is God Himself, who sanctifies them and preserves them in a state of eternal goodness; hence their being rendered unchangeable. Dionysius the Areopagite says: “The angels, not being inclined to move toward evil, but not being motionless, have become totally motionless after the resurrection of Christ not by nature but by grace, for immutability would be to them salvation, since they would no longer fear the change into what is worse and the loss that is thereby incurred. So the Angels have now received the ability to remain unchangeable, having practically learned from the Master the way of salvation and exaltation and assimilation to Him, not by way of pride or conceitedness but of humility or soberness.
|The guardian angel|
12. Are the evil spirits anymore able to return to God?
No! Firstly because their will has been identified with evil and, as a result, they always choose evil; secondly, because they became and have continued to be enemies to God; and thirdly, because they divorced themselves from God, and to be separated from God is eternal death. Indeed, what is death to the sinner is identical with the fall of the evil angels from their rule.
13. How many are the angelic orders, that is, the orders of the heavenly Hierarchy?
The angelic orders are nine, and are divided into three triadic arrangements. The first triad into: Seraphim, Cherubim and Thrones; the second triad into: Dominions Powers and Authorities; and the third triad into: Principalities, Archangels and Angels.
14. What do the Scriptures say about the number of the Angels?
The Scriptures say, that the number of the Angels is very great: “thousands of thousands,” and “myriads of myriads” (Dan. 7:10), “more than ten legions of Angels” (Matth. 6:33), “a multitude of heavenly armies” (Luke 2:13) and “myriads of Angels” (Heb. 12:22).
15. What do the Scriptures say about the power of the Angels?
They say that it is supreme and operates in the spiritual and material cosmos; hence their being called in Scripture “mighty angels” and “excelling in might” (II Thess. 1:7, Ps. 103:20 and II Kings 19:35).
16. What are the occupations of the Angels?
They see the face of God and worship Him, and they also minister to the decisions of the divine Providence (Matth. 18:10, Rev. 5:11, I Pet. 1:12, Gen. 28:12, Acts 12:7,23, Ps. 91:10-12, II Kings 19:35, I Chronicles 16, Matth. 13:30-39 and 25:17).
17. Are the Angels immortal by nature?
No. They are such by grace, because they are creatures of God. John Damascenos says, “an angel is a mindful being … that is immortal not by nature, but by grace; because whatever being has a beginning also has an end by nature; and only God who is everlasting and transcends all everlastingness, etc., is immortal”. 
18. What are the different meanings that the term “angel” has in Scripture?
It means Common Envoys (Job 1:14, Luke 7:24, 9:52), Prophets (Is. 42:19, Mal. 3:1), Priests (Mal. 2:7), sacred preachers of the New Covenant (Rev. 1:20), Impersonal Agencies as, for instance, a pillar of cloud (Ex. 14:9), a Plague (II Sam. 24:16,17), Winds (Ps. 104:4), Pestilence –a name give to the evil angels (Ps. 78:49), a thorn in the flesh of Paul, an angel of Satan (II Cor. 12:7), the second Person of the Holy Trinity: an Angel before Him or an Angel of the Covenant (Is. 63:9, Mal. 3:1). But the word is applied to the heavenly rational beings (Matth. 25: 31).
19. What were the Cherubim?
They were some ideal beings, consisting of four parts, i.e. of man, ox, lion and eagle; the superior face was that of man, but the number of the faces, feet and hands differed according to circumstances (Ezek. 1:6; cf. Ezek. 41:18-19, and Ex. 25:20).
20. What is the etymology of the word Seraphim and what do the Scriptures teach about them?
The word Seraphim denotes something that burns, or glitters, or dazzles, and it appears in Scripture only once (Is. 6:2,6).
21. Is there any proof that angels belongs to different classes?
Yes indeed; 1) from the language of Scripture; Gabriel is distinguished by the fact that he stands before God (Luke 1:19) in some kind of lofty sense; and Michael is referred to as being one of the first archons (Dan. 10:13). In addition, the adjectives, archangels, thrones, principalities, dominions, powers (Jude 9 and Eph. 1:21) bear witness to a variety of classes.
Ss. Archangels' Orthodox Church in Kinshasa, Democratic Republic of Congo (from here). About Orthodox Church in DRC, see here & here.
 Moses does not mention the creation of the Angels in Genesis in the chapters relating to the creation of the cosmos, because his purpose was to teach about the creation of the visible world (See Chrysostom, Ps. 8:4, Iobios the Monk in Photios Bibliotheca Codex 222, p. 591). Athanasius (question 4) says: that he might not provide an excuse to the Jews for idolatry (See Theodoret, question 2 in Difficulties in Genesis and Chrysostom On Genesis Hom. 1). In regard to the time of the creation of the Angels the opinions of the theologians differ. Origen regards the creation of the Angels to have preceded the creation of man and of the sensible cosmos. Gregory the Theologian, Basil the Great, John Chrysostom, John Damascenos and other Fathers teach that Angels were created before the visible creatures. Theodoret holds that they were created on the first day, when, that is, God created heaven and earth according to the first verse of the first chapter. St. Epiphanius also agrees with this view. From Job 38:1 the conclusion is drawn that on the fourth day there were Angels around; because the Lord says to Job: “When the stars were made, all my Angels praised me with a very loud voice.”
The distinction of various orders among the numerous angels (Dan. 7:10, Matth. 26:53, Luke 2:13, Heb. 12:22, Rev. 5:11) is acknowledged, apart from the Fathers (Clement of Rome’s 6:1, 6:16, 7:2, Cyril of Jerusalem’s Catechisms 6:6, 7:11, 11:11, 17:23, Gregory the Theologian’s Oration 34, Damascenos’ Accurate Exposition of the Orthodox Faith II:3, and especially Dionysios the Areopagite’s Heavenly Hierarchy 6 and others) by Holy Scripture itself, which distinguishes: Angels (I Pet. 3:22ff), Archangels (I Thess. 10:16, Jude 9), Cherubim (Gen. 3:24, Rev. 4, 5, 6), Seraphim (Is. 6:2,1), Powers (Eph. 1:21, Rom. 8:31), Thrones, Principalities, Authorities and Dominions (Eph. 1:21, Col. 1:16, Rom. 8:31, Dan. 10:13); and so the Fifth Ecumenical Synod condemned Origen who said among other things, that all the angels were of the same nature and power and only after some of them rebelled were they separated into orders (See Fifth Ecumenical Synod, canons 2 and 14). See also Dan. 7:10, Ps. 96:1, 102:20, 148:2, Rev. 4:1, 7:11-12, Basil the Great’s On Psalm 27, On Isaiah 6, Gregory the Theologian’s Oration 34, Theodoret’s Epitome of the Divine Dogmas 7, John Damascenos’ Accurate Exposition 2:10. Ps. 101:20.
 Damaskenos, Exposition of the Orthodox Faith, II:18.
 On Matthew, ch. 2.
 On First Principles, I:7 and II.
 See The Rudder of St. Nicodemos, p. 131, note 1.
 Damascenos, Exposition of the Orthodox Faith, II:18.
 Satan means enemy, that is, enemy of God and of human beings, of goodness and every virtue, and source of every evil in the world. The word Satan appears five times in the Old Testament. I Chronicles 21, Job 1, Zachariah 3. In the New Testament there are 25 references where the word devil is used in the same sense.
Click here: Synaxis of the Heavenly Bodiless Angelic PowersAngels, Blessed Messengers of God