Dreams—we all have them, even if we do forget them. But what are they exactly? Aristotle gave it them thought. And they certainly became serious business for Rene Descartes who, for a while, lost his epistemic equilibrium over the very idea. Understandable, as dreaming brings up a bunch of deeply philosophical matters that remain largely unresolved—from the nature of consciousness to personal identity and selfhood. Can you really dream that you are someone else?