34 | SCIENTIFIC AMERICAN | SPECIAL EDITION | WINTER 2022

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I

t 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 con-

scious 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 inti-

mate exchanges might as well be carried out via Zoom.

You experience your own mind every waking sec-

ond, 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 first-

hand 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 oth-

ers’ emotions and intentions. But we have a counter-

tendency 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 pro-

posed countless contradictory hypotheses about

what consciousness is and how it arises. Panpsychists

contend that all creatures and even inanimate mat-

ter—even a single proton!—possess consciousness.

Hard-core materialists insist, conversely (and per-

versely), 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—the-

ories of consciousness will remain in the realm of

pure speculation.

But the solipsism problem is far more than a tech-

nical philosophical matter. It is a paranoid but under-

standable response to the feelings of solitude that lurk

within us all. Even if you reject solipsism as an intellec-

tual 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.

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, nov-

elist says, “This is how my life feels” or “This is how life

might feel for another person.” They help us imagine