The Church teaches that God made, besides the visible world, a world of created spirits who serve him and, by his appointment, watch over human life. What she says of them comes from Scripture and the Fathers, and it shapes her worship, from the Mass to the prayer to one’s guardian angel.
The existence of the spiritual, non-corporeal beings that Sacred Scripture usually calls "angels" is a truth of faith. The witness of Scripture is as clear as the unanimity of Tradition.
As purely spiritual creatures angels have intelligence and will: they are personal and immortal creatures, surpassing in perfection all visible creatures, as the splendor of their glory bears witness.
The profession of faith of the Fourth Lateran Council (1215) affirms that God "from the beginning of time made at once (simul) out of nothing both orders of creatures, the spiritual and the corporeal, that is, the angelic and the earthly, and then (deinde) the human creature, who as it were shares in both orders, being composed of spirit and body."
Behind the disobedient choice of our first parents lurks a seductive voice, opposed to God, which makes them fall into death out of envy. Scripture and the Church's Tradition see in this being a fallen angel, called "Satan" or the "devil". The Church teaches that Satan was at first a good angel, made by God: "The devil and the other demons were indeed created naturally good by God, but they became evil by their own doing."
Scripture speaks of a sin of these angels. This "fall" consists in the free choice of these created spirits, who radically and irrevocably rejected God and his reign. We find a reflection of that rebellion in the tempter's words to our first parents: "You will be like God." The devil "has sinned from the beginning"; he is "a liar and the father of lies".
Who are the angels, what is their ministry to men, and what is said of those who fell?
This is the verse of the ninety-first psalm (ninetieth in the Vulgate numbering) in which God gives his angels charge over the one who trusts in him. The Church has read it of the guardianship of the angels. It bears on the teaching that human life is surrounded by the care of the holy angels.
For he hath given his angels charge over thee; to keep thee in all thy ways. In their hands they shall bear thee up: lest thou dash thy foot against a stone.
In the Book of Tobias the angel Raphael makes himself known as one of the seven who stand before the Lord, sent to heal Tobias and to deliver Sara from the devil. It is a scriptural account of an angel sent on a mission to a family. It bears on the angels as God’s messengers to men.
And now the Lord hath sent me to heal thee, and to deliver Sara thy son's wife from the devil. For I am the angel Raphael, one of the seven, who stand before the Lord.
In the Epistle to the Colossians Saint Paul says that all things were created in Christ, visible and invisible, and names thrones, dominations, principalities and powers. The Church reads these as names of the angelic choirs. It bears on the creation of the angels and on Christ as the centre of the angelic world.
For in him were all things created in heaven and on earth, visible and invisible, whether thrones, or dominations, or principalities, or powers. All things were created by him and in him.
The second Epistle of Peter states that God spared not the angels that sinned, but delivered them to be reserved unto judgment. It is a plain witness in the New Testament that some angels fell. It bears on the teaching that the angels who sinned are lost.
For if God spared not the angels that sinned, but delivered them, drawn down by infernal ropes to the lower hell, unto torments, to be reserved unto judgment:
The Epistle of Jude recalls that Michael the archangel, disputing with the devil, durst not bring a judgment of railing speech, but said, “The Lord command thee.” It names the archangel and shows the devil subject to God. It bears on the devil as a creature under God.
When Michael the archangel, disputing with the devil, contended about the body of Moses, he durst not bring against him the judgment of railing speech, but said: The Lord command thee.
The Epistle to the Hebrews says that all the angels of God adore the first begotten Son, and calls them ministering spirits sent to minister for those who shall receive the inheritance of salvation. It bears on the angels as servants of God and on Christ as their centre.
And again, when he bringeth in the first begotten into the world, he saith: And let all the angels of God adore him. And to the angels indeed he saith: He that maketh his angels spirits and his ministers a flame of fire.
Are they not all ministering spirits, sent to minister for them who shall receive the inheritance of salvation?
In the Gospel according to Matthew the Lord says that the angels of the little ones always see the face of his Father in heaven. The Fathers and the Church take it as the chief Gospel text for the guardian angels. It bears on the angels’ watch over human life.
See that you despise not one of these little ones: for I say to you, that their angels in heaven always see the face of my Father who is in heaven.
The Apocalypse of Saint John describes the battle in heaven in which Michael and his angels fight the dragon, who is cast out and called the devil and Satan. The Church reads it of the fall of the rebel angels. It bears on the teaching that the angels who fell have no place in heaven.
And there was a great battle in heaven: Michael and his angels fought with the dragon, and the dragon fought, and his angels. And they prevailed not: neither was their place found any more in heaven. And that great dragon was cast out, that old serpent, who is called the devil and Satan, who seduceth the whole world. And he was cast unto the earth: and his angels were thrown down with him.