Someone wrote us a while ago with this question stating that a visiting priest in their church implied that the devil is a mythical representation or personification of evil. However, this is really misleading and does not reflect in any way the teaching of the Church or even the scriptures.
The traditions and teachings of the Church is rife with evidence in the belief that the devil is real, and even Christ himself demonstrated this belief.
“and Jesus healed many who had various diseases. He also drove out many demons, but he would not let the demons speak because they knew who he was” – Mark 1:34
He replied, “I saw Satan fall like lightning from heaven – Luke 10:18
Remember the temptations?
Then Jesus was led by the Spirit into the wilderness to be tempted by the devil. After fasting forty days and forty nights, he was hungry. The tempter came to him and said, “If you are the Son of God, tell these stones to become bread.”
Jesus answered, “It is written: ‘Man shall not live on bread alone, but on every word that comes from the mouth of God.’”
Then the devil took him to the holy city and had him stand on the highest point of the temple. “If you are the Son of God,” he said, “throw yourself down. For it is written:
“‘He will command his angels concerning you,
and they will lift you up in their hands,
so that you will not strike your foot against a stone.’”
Jesus answered him, “It is also written: ‘Do not put the Lord your God to the test.’”
Again, the devil took him to a very high mountain and showed him all the kingdoms of the world and their splendor. “All this I will give you,” he said, “if you will bow down and worship me.”
Jesus said to him, “Away from me, Satan! For it is written: ‘Worship the Lord your God, and serve him only.’”
Then the devil left him, and angels came and attended him.
The decree of the Fourth Lateran Council contained a statement in its Constitutions that echo the ancient teaching of the Church:
The devil and other demons were created by God naturally good, but they became evil by their own doing. Man, however, sinned at the prompting of the devil.
… All of them will rise with their own bodies, which they now wear, so as to receive according to their deserts, whether these be good or bad; for the latter perpetual punishment with the devil, for the former eternal glory with Christ.
The Sacred Congregation of Divine Worship in the document called “Christian Faith and Demonology” explained the position of the Church by quoting Pope Paul VI:
It is a departure from the picture provided by biblical and Church teaching to refuse to acknowledge the devil’s existence; to regard him as . . . a conceptual and fanciful personification of the unknown causes of our misfortunes. . . . Exegetes and theologians should not be deaf to this warning.
And in 1986 St John Paul II explaining the fall of the angels said:
When, by an act of his own free will, he rejected the truth that he knew about God, Satan became the cosmic “liar and the father of lies” (Jn 8:44). For this reason, he lives in radical and irreversible denial of God and seeks to impose on creation–on the other beings created in the image of God and in particular on people–his own tragic “lie about the good” that is God.