Sleep—which, when things go well, consumes a third of our lives—poses two opposed existential perplexities. The first is about consciousness: we know that we sleep, but cannot know that we are sleeping, since sleep is, in its nature, non-present. The second perplexity has to do with what we can, in fact, remember, and that is the experience of dreams. While engaged in the non-knowable act of sleeping, we also learn nightly that it is possible to know that we have had vivid, intense, unforgettable experiences that are, at the same time, delusions. Sleep tells us that there are black holes outside the possibility of narrative description; the dreams we have when we’re sleeping tell us that our entire existence might be a narrative fiction.