Wait, I thought, the broken wine glass! Or could it be a water glass? At any rate, it is one of the movie’s more famous riddles. The moment is so deliberate and messy and startling — the hotel sequence is for the most part hushed and austere — and yet so arbitrary. In other words, it reeks of symbolism. What was Mr. Kubrick’s point in punctuating his visionary film with something so quotidian?

This is something many critics have chewed over — and me too. I have read that the broken glass was meant to echo the splintered animal bones that become weapons of war in the prehistoric “Dawn of Man” sequence that begins the movie, or that it symbolizes the fragility of existence, or the shattering of the “subject-object” rationality with which homo sapiens traditionally view the world. One essayist divines a reference to “the broken glass of the Judaic marriage ceremony,” a symbol of “the end of one way of life and the beginning of a new one.”