We think of sleep as an interruption of the self. It is a gap in the story of our lives that philosophers from Descartes to Hume have tried to explain away, and that hustle culture would happily abolish. However, philosopher Grace Theodoly argues that this assumes waking consciousness is the baseline and sleep a departure from it. Theodoly argues sleep is what lets us have a coherent story of who we are. Our culture’s drive to eliminate sleep would therefore undermine the very self it hopes to enrich.

On the morning of his great battle against Darius, Alexander the Great overslept. He slept, Montaigne tells us, “so profoundly and so long” that his general Parmenio had to come to his bedside and call him several times by name. He was not the only one. Augustus was fast asleep when the moment came to give the signal for a naval battle. Marius did give his signal, but then lay down under a tree and slept through the flight of his own army.

Montaigne collects these stories in a short essay called “Of Sleep.” He finds it fascinating that even men of the “highest enterprises and most important affairs” will not break their sleep. There is something almost absurd about the spectacle. Great battles are about to begin, and the men charged with fighting them are fast asleep. Montaigne, however, leaves further questioning to scientists, observing that “the physicians may determine whether sleep be so necessary that our lives depend upon it.”

That seemed satisfactory enough for Montaigne. But should it be? Science explains that sleep is necessary for biological mechanisms like synaptic pruning and metabolic clearance, and that it serves the broader purpose of restoration. These explanations address physiological and teleological questions about sleep, but they do not address the inherent strangeness of the arrangement. That restoring ourselves should require the total extinction of subjective awareness on a daily basis, amounting to a third of our lives, is puzzling. Our bodies do plenty of maintenance while we are awake; the lights are on when we digest or fight infections. Why shouldn’t all of it work that way? This peculiarity raises a third kind of question, an ontological question, which inquires into the essential nature of sleep and what it means for the self. It asks why sustaining conscious experience should require the periodic suspension sleep demands, and whether that suspension sits in tension with the way in which we understand ourselves as selves.

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It is this question that I am concerned with here, and it is almost as difficult to pin down as it is to answer. The question eludes us because our understanding of sleep is so thoroughly mediated by its restorative function that we tend to overlook what is strange about the state itself. The Merriam-Webster Dictionary defines sleep as the periodic “loss of consciousness of one’s surroundings” that is “usually considered essential to the restoration and recovery of vital bodily and mental functions.” What is striking about this definition is that sleep is understood through its contribution to waking life, rather than as a state of existence in its own right.