Because this collection called Remembrance of Things Past is essentially the philosophical journey of Marcel, his issues with sleep are definitively significant in the stories here. In short, we find out fairly early that sleep connects Marcel with ancient philosophers, allows him to contemplate his own life, and allows the reader to be introduced to new characters in the series. The long and the short of Proust’s use of time is that sometimes it is time that is lost and sometime it is time that is remembered.
Appropriately, we first find Marcel in bed, unaware of his surroundings, and unable to sleep due to his thoughts in Proust’s first volume called Swann’s Way. Marcel’s insomnia remains as he remembers a pivotal childhood experience: his mom stays with the young Marcel one night when he is unable to sleep. It is this memory that disturbs Marcel’s sense of time as we know it and that allows Marcel’s remembrances to interact with each other. As should be expected, this is a man who had an interesting (and somewhat disturbing) childhood that led into becoming quiet dissolution in his middle age.
This original idea of the discontinuity of sleep (where the person isn’t sure if he or she is actually reading or thinking or walking or remembering) is supposed to remind the reader of the ancient philosophers and, especially in this case, René Descartes. It is the catalyst that gets Proust into the other aspects of plot in his volume series because in Marcel’s insomnia is where he remembers the other characters and other pieces of setting. We begin to wonder whether Marcel is truly experiencing insomnia or simply dreaming.
If a little dreaming is dangerous, the cure for it is not to dream less, but to dream more, to dream all the time.
Insomnia is the only way that we, as readers, are presented with a more traditional plot; therefore, it is appropriate that insomnia is a constant problem for Marcel. In these insomniac musings, we learn of many things. We learn of the provincial village of Combray where Marcel’s great-aunt lived. We learn of a vacation with Marcel’s grandma in Balbec. We learn about Saint-Loup in the military and stationed in Paris. We learn about Marcel’s trip to see his mother in Venice, Italy. Being exposed to a characters’ thoughts via insomnia is a most unusual way to be presented with ideas and should make the reader question them continually.
In conclusion, I have to mention that my response is about the denotation of sleep as the time when a human body gets its rest. I realize that, due to Marcel’s many encounters both with women and men in different sexual relationships (including homosexuality), you could be asking about a different definition of sleep. In your question if you are referencing sleep as “sleeping with” someone in regards to the act of making love, please repost your question.