Question Four
Whether those whom we call souls are souls, or rather demons - apostate spirits enclosed in bodies so that they may be purged there
It is asked whether those whom we call souls are not souls but demons - apostate spirits enclosed in bodies so that they may be purged there - as Cyril says.
Certain persons answered this simply by saying that those whom we call souls in human bodies are not souls, but reprobate spirits and apostate angels, that is, demons enclosed in human bodies so that they may be purged there. They are said to pass from body to body, so that, if they had not repented and had not been purged in one body, they might repent and be purged in another. But this opinion is ridiculous and errs in three ways.
First, because it maintains that demons are to be saved through repentance. Against this it is said in Matthew 25: “Go, you accursed, into everlasting fire.”
Second, because it maintains that there are no souls, contrary to Matthew 11: “In your patience you shall possess your souls.”
Third, because it says that demons are enclosed in all human bodies, which is the saying of a foolish person. For it is foolish to concede that demons dwell where the Holy Spirit dwells. But the Holy Spirit dwells in human minds and bodies, according to 1 Corinthians 14: “Do you not know that your members are the temple of the Holy Spirit?” Therefore their opinion is false and heretical, and deservedly to be rejected.
Addition
Augustine marvels very greatly at this error when he attacks the Platonists who thought that human souls were demons after [leaving] their bodies. See Augustine, Book IX of The City of God, chapter 11.