The Clementine Homilies by Unknown
Chapter XVI.--None But Evil Demons Appear to the Impious.
And Peter said: |I remember that I promised to prove this point, and to give my proofs in regard to it from Scripture and apart from Scripture. And now listen to what I say. We know that there are many (if you will pardon me the statement; and if you don't, I can appeal to those who are present as judges) who worship idols, commit adultery, and sin in every way, and yet they see true visions and dreams, and some of them have also apparitions of demons. For I maintain that the eyes of mortals cannot see the incorporeal form of the Father or Son, because it is illumined by exceeding great light. Wherefore it is not because God envies, but because He pities, that He cannot be seen by man who has been turned into flesh. For he who sees God cannot live. For the excess of light dissolves the flesh of him who sees; unless by the secret power of God the flesh be changed into the nature of light, so that it can see light, or the substance of light be changed into flesh, so that it can be seen by flesh. For the power to see the Father, without undergoing any change, belongs to the Son alone. But the just shall also in like manner behold God; for in the resurrection of the dead, when they have been changed, as far as their bodies are concerned, into light, and become like the angels, they shall be able to see Him. Finally, then, if any angel be sent that he may he seen by a man, he is changed into flesh, that he may be able to be seen by flesh. For no one can see the incorporeal power not only of the Son, but not even of an angel. But if one sees an apparition, he should know that this is the apparition of an evil demon.