Revelation Concerning the Angels of Christian Angelology
FROM THE FUNDAMENTALS OF CATHOLIC DOGMA
§ 27. The Nature of the Angels
2. Natural immortality of the Angels
The Angels are by nature immortal [Sent. communis.]
The natural immortality of the Angels flows from the pure spirituality of their nature. Cf. Luke 20:36: "Neither can they [the resurrected] die any more for they are equal to the Angels." The blessedness of the good Angels, and the rejection of the bad Angels is, according to the testimony of Revelation, of eternal duration. Matt. 18:20: "I say to you that their Angels in Heaven always see the face of My Father, Who is in Heaven." Matt. 25:41: "Depart from ye cursed, into everlasting fire, which was prepared for the devil and His Angels."
The view put forward by St. John Damascene [de fide orth. II 3] and by many Schoolmen [Scotus, Biel] that the immortality of the Angels is a gift of grace is unsound, for in reality immortality is a necessary consequence of their spiritual nature. S. th. I 50:5.