Tertullian

“ Accordingly, when the body shakes off its slumber, it asserts before your eye the resurrection of the dead by its own resumption of its natural functions. Such, therefore, must be both the natural reason and the reasonable nature of sleep. If you only regard it as the image of death, you initiate faith, you nourish hope, you learn both how to die and how to live, you learn watchfulness, even while you sleep. ”

“ He accordingly sets before your view the human body stricken by the friendly power of slumber, prostrated by the kindly necessity of repose immoveable in position, just as it lay previous to life, and just as it will lie after life is past: there it lies as an attestation of its form when first moulded, and of its condition when at last buried—awaiting the soul in both stages, in the former previous to its bestowal, in the latter after its recent withdrawal. ”

“ Since, then, sleep is indispensable to our life, and health, and succour, there can be nothing pertaining to it which is not reasonable, and which is not natural. Hence it is that physicians banish beyond the gateway of nature everything which is contrary to what is vital, healthful, and helpful to nature; for those maladies which are inimical to sleep—maladies of the mind and of the stomach—they have decided to be contrariant to nature, and by such decision have determined as its corollary that sleep is perfectly natural. ”

“ Moreover, when they declare that sleep is not natural in the lethargic state, they derive their conclusion from the fact that it is natural when it is in its due and regular exercise. For every natural state is impaired either by defect or by excess, whilst it is maintained by its proper measure and amount. That, therefore, will be natural in its condition which may be rendered non-natural by defect or by excess. Well, now, what if you were to remove eating and drinking from the conditions of nature? if in them lies the chief incentive to sleep. ”

“ For as Adam was a figure of Christ, Adam’s sleep shadowed out the death of Christ, who was to sleep a mortal slumber, that from the wound inflicted on His side might, in like manner (as Eve was formed) , be typified the church, the true mother of the living. This is why sleep is so salutary, so rational, and is actually formed into the model of that death which is general and common to the race of man. ”

“ In like manner, the immortality of the soul precludes belief in the theory that sleep is an intermission of the animal spirit, or an indigence of the spirit, or a separation of the (soul’s) connatural spirit. ”

“ He, therefore, who shall doubt whether sleep is a natural function, has the dialectical experts calling in question the whole difference between things natural and supernatural—so that what things he supposed to be beyond nature he may, (if he likes,) be safe in assigning to nature, which indeed has made such a disposition of things, that they may seemingly be accounted as beyond it ”

“ Indeed, we cannot possibly believe that sleep is a weariness; it is rather the opposite, for it undoubtedly removes weariness, and a person is refreshed by sleep instead of being fatigued. Besides, sleep is not always the result of fatigue ”

“ Nor can I allow that sleep is a cooling or decaying of the animal heat, for our bodies derive warmth from sleep in such a way that the regular dispersion of the food by means of sleep could not so easily go on if there were too much heat to accelerate it unduly, or cold to retard it, if sleep had the alleged refrigerating influence. ”