Lactantius

“ Therefore it is called away by images, [8] until the limbs, bedewed with sleep, are invigorated; for the body while the perception is awake, although it lies motionless, yet is not at rest, because the perception burns in it, and vibrates as a flame, and keeps all the limbs bound to itself.
But when the mind is transferred from its application to the contemplation of images, then at length the whole body is resolved into rest. But the mind is transferred from dark thought, when, under the influence of darkness, it has begun to be alone with itself. ”

“ For narratives often testify that there have been dreams which have had an immediate and a remarkable accomplishment, [12] and the answers of our prophets have been after the character of a dream. [13] On which account they are not always true, nor always false, as Virgil testified, [14] who supposed that there were two gates for the passage of dreams. But those which are false are seen for the sake of sleeping; those which are true are sent by God, that by this revelation we may learn impending goods or evils. ”

“ For as the mind is diverted in the day by true sights, so that it does not sleep; so is it diverted in the night by false sights, so that it is not aroused. For if it perceives no images, it will follow of necessity either that it is awake, or that it is asleep in perpetual death. ”