There is a thought most people have had and almost nobody admits to. The thought that other people might not be real. Not in a psychotic sense. Not in a way that requires medication or concern. In the way that arrives at 3am or in the middle of a conversation that should matter more than it does, when someone is telling you something painful and you are nodding and your face is doing the right things and somewhere behind your eyes there is a cold, flat nothing. Not cruelty. Not indifference, exactly. Something worse. The suspicion that whatever is happening inside them is not happening the way it happens inside you. That the lights might be on but the room might be empty. That you are the only one in here.
Philosophy has a word for this. Solipsism. From the Latin solus, alone, and ipse, self. The self, alone. It is usually presented as an extreme position that nobody holds: the idea that only your own mind can be known to exist, that everything else might be scenery. Undergraduates encounter it in epistemology tutorials and treat it as an intellectual toy, a puzzle to be solved and shelved. But the reason it keeps resurfacing across twenty-five centuries of thought is not because it is a good puzzle. It is because it describes something that happens in the body before it ever reaches the seminar room.
When other people's pain doesn't land
Descartes lit the fuse. His method of radical doubt stripped away everything that could be doubted, the senses, the body, the external world, until only the thinking thing remained. Cogito ergo sum. I think, therefore I am. It was supposed to be a foundation, a rock to build certainty on. But the rock had a crack in it from the start: if the only certainty is that you are thinking, everything else is reconstruction. Other minds included. Other suffering included. The whole architecture of human connection resting on ground that Descartes admitted he could not verify.
The moments where solipsism stops being philosophy and starts being experience are not grand. They are domestic. Sitting across from a friend who is crying and feeling nothing travel across the gap between you. Watching the news and registering the numbers without the weight arriving. Standing in a crowd and feeling not lonely but ontologically separate, as if the crowd were projected onto a surface you are watching from behind glass. These moments do not mean you are broken. They mean consciousness is doing what consciousness does: running its operations inside a sealed unit and occasionally noticing the seal. The digital loneliness paradox amplifies this: more connection, more glass.
The problem is not that other minds don't exist
Wittgenstein took a different route to the same wall. His argument against solipsism was not that it was wrong but that it was meaningless. If you say "only my experience is real," you are using language, and language is shared. The tools you use to articulate solipsism were built by other minds, absorbed from other mouths, shaped by interactions you cannot account for without granting those others some form of reality. His private language argument: there is no such thing as a language only one person speaks. Meaning requires use, use requires community, community requires other minds. You cannot coherently deny other minds using the products of other minds.
But coherence was never the point. Solipsism is not an argument. It is a sensation. And sensations do not care whether they are logically coherent. The feeling of being enclosed inside your own experience is not refuted by the observation that your experience was socially constructed. If anything, that makes it worse. The cage was built by others, but you are the only one inside it.
Thomas Nagel came at the problem from the side. His question was not whether other minds exist but whether you could ever access one. "What is it like to be a bat?" was not about bats. It was about the impossibility of stepping outside your own experiential structure and into another. You can imagine hanging upside down. You can imagine echolocation. But you are imagining it as a human imagining it, and the bat-ness of being a bat is exactly what escapes that exercise. The subjective character of experience is locked to the subject. You can never inhabit it from outside. Applied to the people closest to you, it means you will never know what it is like to be your partner, your child, your oldest friend. You will know what it is like to be you, imagining what it might be like to be them. The map is always yours.
The face that makes the question irrelevant
Levinas understood that the exit from solipsism is not intellectual. It is ethical. The face of the other, he said. Not the face as a set of features to be read for information. The face as a demand. The other person's face, when you actually encounter it rather than process it, makes a claim on you that precedes your ability to categorise or comprehend it. Before you can decide whether the other mind is real, before you can run your epistemological checks, the face has already called you into responsibility. It does not ask you to believe in its reality. It confronts you with a demand that makes the question disappear. There is a version of this in Buber's I-Thou, the moment where the other stops being scenery and becomes a presence.
Levinas was not offering proof. He was pointing at something that happens before proof becomes necessary. The encounter with the other, when it is actual and not performed, when it arrives without your defences having time to arrange themselves, does not resolve the philosophical problem of solipsism. It bypasses it. For a moment you are not wondering whether the other is real. You are responding to them. The responding is prior to the doubting.
R.D. Laing saw the clinical weather of this. People whose sense of their own existence had never solidified enough to stop being a question. For whom the reality of others was not a settled matter but a daily negotiation conducted from inside a self that felt provisional, permeable, at risk of dissolving if they looked at it too directly. The solipsistic moment, for these people, is not an intellectual game. It is the temperature of the room they live in. The doubt about other minds is inseparable from the doubt about their own.
And this is where it folds. The coldest version of solipsism says: I am the only real thing. But the lived texture of it says something else entirely. It says: I cannot reach anything outside myself, and I am not certain there is a self to reach inside, either. The loneliness does not point in one direction. It curves back. The same closure that separates you from others separates you from whatever you are underneath the accumulated performance. You are sealed in, but what you are sealed in with is a stranger.
Descartes thought he had found the one thing he could not doubt. The thinking thing. The I that thinks. But even that dissolves under enough pressure. Who is the I? The one doing the thinking, or the one watching the thinking happen? The cogito gives you a verb, not a subject. Something is thinking. You are alone with something you cannot identify, in a room with no windows, and the walls might be painted on.
Nobody lives inside solipsism as a settled position. But everyone visits. The question is not whether other people are real. The question is what it means that the thought can arise at all, that consciousness can produce the suspicion that it is the only consciousness, that the architecture of experience allows for the possibility that nothing exists beyond the experiencing. Not as a theory to be debated. As a weather pattern that moves through and leaves you sitting in a room full of people, smiling, while something behind the smile is checking the walls for seams.