It is a central dilemma of human life—more urgent, arguably, than the inevitability of suffering and death. I have been brooding and ranting to my students about it for years. It surely troubles us more than ever during this plague-ridden era. Philosophers call it the problem of other minds. I prefer to call it the solipsism problem. Solipsism, technically, is an extreme form of skepticism, at once utterly illogical and irrefutable. It holds that you are the only conscious being in existence. The cosmos sprang into existence when you became sentient, and it will vanish when you die. As crazy as this proposition seems, it rests on a brute fact: each of us is sealed in an impermeable prison cell of subjective awareness. Even our most intimate exchanges might as well be carried out via Zoom.
You experience your own mind every waking second, but you can only infer the existence of other minds through indirect means. Other people seem to possess conscious perceptions, emotions, memories, intentions, just as you do, but you cannot be sure they do. You can guess how the world looks to me based on my behavior and utterances, including these words you are reading, but you have no firsthand access to my inner life. For all you know, I might be a mindless bot.
Natural selection instilled in us the capacity for a so-called theory of mind—a talent for intuiting others’ emotions and intentions. But we have a countertendency to deceive one another and to fear we are being deceived. The ultimate deception would be pretending you are conscious when you are not.
The solipsism problem thwarts efforts to explain consciousness. Scientists and philosophers have proposed countless contradictory hypotheses about what consciousness is and how it arises. Panpsychists contend that all creatures and even inanimate matter—even a single proton!—possess consciousness. Hard-core materialists insist, conversely (and perversely), that not even humans are all that conscious.
The solipsism problem prevents us from verifying or falsifying these and other claims. I cannot be certain that you are conscious, let alone a jellyfish, bot or doorknob. As long as we lack what neuroscientist Christof Koch has called a consciousness meter—a device that can measure consciousness in the same way that a thermometer measures temperature—theories of consciousness will remain in the realm of pure speculation.
But the solipsism problem is far more than a technical philosophical matter. It is a paranoid but understandable response to the feelings of solitude that lurk within us all. Even if you reject solipsism as an intellectual position, you sense it, emotionally, whenever you feel estranged from others, whenever you confront the awful truth that you can never know—really know—another person, and no one can really know you.
Natural selection instilled in us the capacity for a so-called theory of mind—a talent for intuiting others’ emotions and intentions. But we have a countertendency to deceive one another and to fear we are being deceived.
Religion is one response to the solipsism problem. Our ancestors dreamed up a supernatural entity who bears witness to our innermost fears and desires. No matter how lonesome we feel, how alienated from our fellow humans, God is always there watching over us. He sees our souls, our most secret selves, and He loves us anyway. Wouldn’t it be nice to think so?
The arts, too, can be seen as attempts to overcome the solipsism problem. The artist, musician, poet, novelist says, “This is how my life feels” or “This is how life might feel for another person.” They help us imagine what it is like to be a Black woman trying to save her children from slavery or a Jewish ad salesman wandering through Dublin, wondering whether his wife is cheating on him. But to imagine is not to know.
Some of my favorite works of art dwell on the solipsism problem. In I’m Thinking of Ending Things and earlier films, as well as his novel Antkind, Charlie Kaufman depicts other people as projections of a disturbed protagonist. Kaufman no doubt hopes to help us, and himself, overcome the solipsism problem by venting his anxiety about it, but I find his dramatizations almost too evocative.
Love, ideally, gives us the illusion of transcending the solipsism problem. You feel you really know someone, from the inside out, and they know you. In moments of ecstatic sexual communion or mundane togetherness—while you’re eating pizza and watching The Alienist, say—you fuse with your beloved. The barrier between you seems to vanish.
Inevitably, however, your lover disappoints, deceives, betrays you. Or, less dramatically, some subtle biocognitive shift occurs. You look at her as she nibbles her pizza and think, Who, what, is this odd creature? The solipsism problem has reemerged, more painful and suffocating than ever.
It gets worse. In addition to the problem of other minds, there is the problem of our own. As evolutionary psychologist Robert Trivers points out, we deceive ourselves at least as effectively as we deceive others. A corollary of this dark truth is that we know ourselves even less than we know others.
If a lion could talk, philosopher Ludwig Wittgenstein said, we couldn’t understand it. The same is true, I suspect, of our own deepest selves. If you could eavesdrop on your subconscious, you would hear nothing but grunts, growls and moans—or perhaps the high-pitched squeaks of raw machine-code data coursing through a channel.
For the mentally ill, solipsism can become terrifyingly vivid. Victims of Capgras syndrome think that identical imposters have replaced their loved ones. If you have Cotard’s delusion, also known as walking corpse syndrome, you become convinced that you are dead. A much more common disorder is derealization, which makes everything—you, others, reality as a whole—feel strange, phony, simulated.
Derealization plagued me throughout my youth. One episode was self-induced. Hanging out with friends in high school, I thought it would be fun to hyperventilate, hold my breath and let someone squeeze my chest until I passed out. When I woke up, I didn’t recognize my buddies. They were demons jeering at me. For weeks after that horrifying sensation faded, everything still felt unreal, as if I were in a dreadful movie.
What if those afflicted with these alleged delusions actually see reality clearly? According to the Buddhist doctrine of anatta, the self does not really exist. When you try to pin down your own essence, to grasp it, it slips through your fingers.
We have devised methods for cultivating self-knowledge and quelling our anxieties, such as meditation and psychotherapy. But these practices strike me as forms of self-brainwashing. When we meditate or see a therapist, we are not solving the solipsism problem. We are merely training ourselves to ignore it, to suppress the horror and despair that it triggers.
We have also invented mythical places in which the solipsism problem vanishes. We transcend our solitude and merge with others into a unified whole. We call these places heaven, nirvana, the Singularity. But solipsism is a cave from which we cannot escape—except, perhaps, by pretending it does not exist. Or, paradoxically, by confronting it, the way Kaufman does. Knowing we are in the cave may be as close as we can get to escaping it.
Conceivably, technology could deliver us from the solipsism problem. Koch proposes that we all get brain implants with Wi-Fi so we can meld minds through a kind of high-tech telepathy. Philosopher Colin McGinn suggests a technique that involves “brain splicing,” transferring bits of your brain into mine, and vice versa.
But do we really want to escape the prison of our subjective selves? The archnemesis of Star Trek: The Next Generation is the Borg, a legion of tech-enhanced humanoids who have fused into one big meta-entity. Borg members have lost their separation from one another and hence their individuality. When they meet ordinary humans, they mutter in a scary monotone, “You will be assimilated. Resistance is futile. ”
As hard as solitude can be for me to bear, I do not want to be assimilated. If solipsism haunts me, so does oneness, a unification so complete that it extinguishes my puny mortal self. Perhaps the best way to cope with the solipsism problem in this weird, lonely time is to imagine a world in which it has vanished.
John Horgan, who has written for Scientific American since 1986, comments on science on his free online journal Cross-Check. He has also posted his books Mind-Body Problems and My Quantum Experiment online. Horgan teaches at Stevens Institute of Technology.