3 But what can be the reason that they love also to dwell in the tombs? They would fain suggest to the multitude a pernicious opinion, as though the souls of the dead become demons, which God forbid we should ever admit into our conception. “But what then will you say,” one may ask, “when many of the sorcerers take children and slay them, in order to have the soul afterwards to assist them?” Why, whence is this evident? For of their slaying them, indeed, many tell us, but as to the souls of the slain being with them, whence do you know it, I pray you? “The possessed themselves,” it is replied, “cry out, I am the soul of such a one.” But this too is a kind of stage-play, and devilish deceit. For it is not the spirit of the dead that cries out, but the evil spirit that feigns these things in order to deceive the hearers. For if it were possible for a soul to enter into the substance of an evil spirit, much more into its own body.
And besides, it stands not to reason that the injured soul should co-operate with the wrong-doer, or that a man should be able to change an incorporeal power into another substance. For if in bodies this were impossible, and one could not make a man's body become that of an ass; much more were this impossible in the invisible soul; neither could one transform it into the substance of an evil spirit. So that these are the sayings of besotted old wives, and spectres to frighten children.
Nor indeed is it possible for a soul, torn away from the body, to wander here any more. For “the souls of the righteous are in the hand of God;” and if of the righteous, then those children's souls also; for neither are they wicked: and the souls too of sinners are straightway led away hence. And it is evident from Lazarus and the rich man; and elsewhere too Christ says, “This day they require your soul of you.” And it may not be that a soul, when it is gone forth from the body, should wander here; nor is the reason hard to see. For if we, going about on the earth which is familiar and well known to us, being encompassed with a body, when we are journeying in a strange road, know not which way to go unless we have some one to lead us; how should the soul, being rent away from the body, and having gone out from all her accustomed region, know where to walk without one to show her the way?
And from many other things too one might perceive, that it is not possible for a disembodied soul to remain here. For both Stephen says, “Receive my spirit;” and Paul, “To depart and to be with Christ is far better;” and of the patriarch too the Scripture says, that “he was gathered unto his fathers, being cherished in a good old age.” And as to the proof, that neither can the souls of sinners continue here; hear the rich man making much entreaty for this, and not obtaining it; since had it been at all possible, he would have come, and have told what had come to pass there. Whence it is evident that after their departure hence our souls are led away into some place, having no more power of themselves to come back again, but awaiting that dreadful day.
Source: Homilies on the Gospel of St. Matthew (New Advent)