Mainstream psychology, and nearly every feature of modern life, puts a strong emphasis on the healthy ego. It’s a comforting, whole-wheat kind of idea, an essential part of any balanced personality. We all know we can have too little self-love, too little self-care. By all means, put yourself first, set the boundaries, don the moisturizing face mask. The opposite message, that there is such a thing as too much self-love or self-concern, is not widely circulated on TikTok. But obviously, everything has its limits.

What happens when the limits are off? Bad things, I’m sorry to say. Frightful things. The reflected self is rarely reassuring for long. Across cultures, mirrors have been used by soothsayers, sorcerers and witches for scrying, divination and attempts to peer beyond the visible world. In folklore and occult practice, the mirror is not merely reflective but permeable — a portal where something might appear, or someone may return.

Even the postmodernists have their own warnings. In 1967, Michel Foucault darkly described the mirror as a kind of threshold, a mix between a fantasy world, a utopia and some weird other place on the margins — which he called a “heterotopia.” The mirror is one such strange place because we discover our presence and our absence at the same time. “I see myself there where I am not,” he wrote, “in an unreal, virtual space that opens up behind the surface.”

Some other heterotopias, according to Foucault, include the honeymoon trip, psychiatric hospitals, vacation villages, prisons, the theater, the cinema, museums, libraries, brothels and the cemetery. In these settings, the normal order of things breaks down and certain truths are exposed. Each of these places could serve as an apt metaphor for the screens, monitors and social media applications that relentlessly reflect us back to ourselves. This technology is a mirror, but it is also a museum, a theater, a prison.