You’re halfway through an ordinary conversation when something shifts. The words. The light in the room. The exact way someone tilts their head. For a moment, you feel certain you’ve lived this scene before. Then the feeling disappears. That strange sense of familiarity is called déjà vu, French for “already seen.” Almost everyone experiences it at some point. But what causes it? Is it a memory glitch, a spiritual sign, or something worth paying closer attention to? What caus