For the light which is the object of our senses does not shine in darkness, but apart from it; but the preaching of Christ has shone forth in the midst of prevailing error, and made it to disappear.
-St. John Chrysostom, Homily 5 on John 1, 4th Century


But how is this effected? Then when we have cleansed the soul from all the passions. For sin is darkness, and a deep darkness; as is clear, because men do it unconsciously and secretly.
-St. John Chrysostom, Homily 5 on John 1, 4th Century