Soon as the force of that fallacious Fruit,The passage from innocence to experience is at the same time a renunciation of the light and dreamless sleep of the pure. The feeling of sleep as a gross burden reflects the ever-increasing weight of concern that preoccupies the civilized man after the Fall; the innocent sleep lightly because they have nothing to worry about, no future to predict with dreams.
That with exhilerating vapour bland
About thir spirits had plaid, and inmost powers
Made erre, was now exhal'd, and grosser sleep
Bred of unkindly fumes, with conscious dreams
Encumberd, now had left them, up they rose
As from unrest, and each the other viewing,
Soon found thir Eyes how op'nd, and thir minds
How dark'nd; innocence, that as a veile
Had shadow'd them from knowing ill, was gon.
- Milton, Paradise Lost
Seul, oisif, et toujours voisin du danger, l'homme sauvage doit aimer à dormir, et avoir le sommeil léger comme les animaux, qui, pensant peu, dorment, pour ainsi dire, tout le temps qu'ils ne pensent point. Sa propre conservation faisant presque son unique soin, ses facultés les plus exercées doivent être celles qui ont pour objet principal l'attaque et la défense, soit pour subjuguer sa proie, soit pour se garantir d'être celle d'un autre animal: au contraire, les organes qui ne se perfectionnent que par la mollesse et la sensualité doivent rester dans un état de grossièreté, qui exclut en lui toute espèce de délicatesse; et ses sens se trouvant partagés sur ce point, il aura le toucher et le goût d'une rudesse extrême; la vue, l'ouïe et l'odorat de la plus grande subtilité.
- Rousseau, Discours sur les origines de l'inegalité
Now know I well what people sought formerly above all else when they sought teachers of virtue. Good sleep they sought for themselves, and poppy-head virtues to promote it! To all those belauded sages of the academic chairs, wisdom was sleep without dreams: they knew no higher significance of life. Even at present, to be sure, there are some like this preacher of virtue, and not always so honorable: but their time is past. And not much longer do they stand: there they already lie.
- Nietzsche, Thus Spoke Zarathustra
But the advocacy of this light sleep undermines the fundamental moralism of Milton, and, to a lesser extent, Rousseau. Their goal is always to show that the physical manifestations of the state of innocence, of noble savagery, are reflections of an underlying moral virtue: the savage isn't just different because he does not seek for civilized entertainment, but better because more virtuous. The use of the sleep image serves to push this argument in the reverse direction: the advantage of morality and virtue is that it permits an easier and lighter sleep.
This process of reversal is, of course, what Nietzsche has in mind. The "chairs of virtue" are occupied by those who pretend to speak for or represent morality but really only represent a lighter sleep and an easier digestion; the ridiculousness of the particular prophet in this chapter is only the ridiculousness of the others made manifest. The problem of the reversal is more serious for Rousseau than for Milton, however, though the latter may represent Christianity. For Rousseau elsewhere preaches the Spartan renunciation of bodily comfort, condemning luxury in part as a constant and never-ending pursuit of physical gratification. Yet, when he describes the noble savage as one who sleeps lightly and easily, what is he advertising if not the sensual advantages of the state of nature? The argument from physical pleasure cannot but conflict with the argument from virtue.
Ultimately, too, the sleep without dreams represents something darker and less pleasant to contemplate: the renunciation of the intellect, which for Rousseau (and sometimes for Nietzsche) is always an explicit goal, but for Milton more often a threat. The commentaries underneath my copy of Paradise Lost suggest the ultimate "moral import" of the Fall to be the defeat of reason in favor of sensuality. But can a creature whose sleep is dreamless like an animal's (and who has no knowledge of good and evil) even be said to possess that capacity to refuse its immediate desires?
Reason is something that only comes with Blake's second birth. And the twice-born is cursed to look back on the naivety of the first and sentimentalize it. Thus the innocent one cannot know the advantages of his strong digestion and light sleep; that comes only later. This is, in a sense, ironic. The argument from the physical, which asks us to give up the dreams of the second birth, becomes immediately incomprehensible once it is followed through to its conclusion. This argument is as much of a parasite on the knowledge of good and evil as any of its more intellectualized counterparts.