Upvote:1
Regarding the first article of the Creed, "I believe in God the Father almighty, creator of heaven ['the world of spirits'] and of earth" (cf. Genesis 1:1), the Catechism of the Council of Trent Β§1.1 explains that God created man last, after "He created out of nothing the spiritual world and Angels," which included the devil:
Lastly, He formed man from the slime of the earth
So, yes, the devil did preexist humans.
Upvote:2
Job tells of the time when the universe was created, and the angels sang and praised his work:
Tell me, since thou art so wise, was it thou or I designed earthβs plan, measuring it out with the line? How came its base to stand so firm; who laid its corner-stone? To me, that day, all the morning stars sang together, all the powers of heaven uttered their joyful praise. -- New Advent -- Job 38:5-7
These spirit beings (stars are symbolic of angels) obviously preceded the creation of mankind.
The Catholic Encyclopedia contains a long article about the Devil, giving great detail about Satan and his fallen angels. In particular:
... the words of St. Jude: "And the angels who kept not their principality, but forsook their own habitation, he hath reserved under darkness in everlasting chains, unto the judgment of the great day" (Jude 1:6; cf. 2 Peter 2:4).
In the Old Testament we have a brief reference to the Fall in Job 4:18: "In his angels he found wickedness". But to this must be added the two classic texts in the prophets:
How art thou fallen from heaven, O Lucifer, who didst rise in the morning? how art thou fallen to the earth, that didst wound the nations? And thou saidst in thy heart: I will ascend into heaven, I will exalt my throne above the stars of God, I will sit in the mountain of the covenant, in the sides of the north. I will ascend above the height of the clouds, I will be like the most High. But yet thou shalt be brought down to hell, into the depth of the pit. (Isaiah 14:12-15)
This parable of the prophet is expressly directed against the King of Babylon, but both the early Fathers and later Catholic commentators agree in understanding it as applying with deeper significance to the fall of the rebel angel. And the older commentators generally consider that this interpretation is confirmed by the words of Our Lord to his disciples: "I saw Satan like lightning falling from heaven" (Luke 10:18). For these words were regarded as a rebuke to the disciples, who were thus warned of the danger of pride by being reminded of the fall of Lucifer.
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The parallel prophetic passage is Ezekiel's lamentation upon the king of Tyre:
You were the seal of resemblance, full of wisdom, and perfect in beauty. You were in the pleasures of the paradise of God; every precious stone was thy covering; the sardius, the topaz, and the jasper, the chrysolite, and the onyx, and the beryl, the sapphire, and the carbuncle, and the emerald; gold the work of your beauty: and your pipes were prepared in the day that you were created. You a cherub stretched out, and protecting, and I set you in the holy mountain of God, you have walked in the midst of the stones of fire. You were perfect in your wave from the day of creation, until iniquity was found in you. (Ezekiel 28:12-15)
The spiritual creation and later Lucifer's rebellion and fall obviously occurred before the seven days of creation.
... it is clearly taught that the Devil and the other demons are spiritual or angelic creatures created by God in a state of innocence, and that they became evil by their own act.