What is it like to be you?

Nearly 50 years ago the philosopher Thomas Nagel postulated a thought experiment called, “What Is It Like To Be A Bat?” that quickly became one the most influential contributions to the sub-field of consciousness studies called “philosophy of mind.”

Today, as one half of America tears its hair out trying to figure out why the other half thinks the way it does, Nagel’s experiment is particularly relevant. Revisiting the insights into the human psyche that it spawned, may help us understand the underpinnings of the communications gap.

Nagel’s experiment was designed to probe the nature of experience, specifically the nature of “subjective experience” as distinct from the biological sensory process of “objective experience” of the world around us.

But why bats? Nagel illustrated the difference between objective and subjective experience with the help of what he called a “fundamentally alien form of life,” a mammal like us, capable of experience, but with “a range of activity and a sensory apparatus so different from ours that the problem I want to pose is exceptionally vivid.”

Bats, as you may know, possess a most unusual sensory apparatus. Bats do have eyes, but they “see” the world primarily by echolocation (sonar). They emit ultrasonic sound waves that bounce off objects in their environment; by correlating the echoes with the outgoing signals they can recognize distance, shape and size.

“Bat sonar, though clearly a form of perception, is not similar in its operation to any sense that [humans] possess, and there is no reason to suppose that it is subjectively like anything we can experience or imagine.”

Nagel’s premise was that while we may observe — and measure — the biological processes underlying a bat’s echolocating capability, the experience of it lies beyond our ken. We humans simply cannot know “what it feels like” to be a bat. It may be possible for us to imagine what it would be like to fly, to navigate by sonar — or to hang upside down and to eat insects — but that wouldn’t be the same thing as a bat’s perspective; it would be a human perspective on what a bat may feel. Only being born as a bat makes for a bat’s experience of itself — its subjective experience.

Nagel argued that subjective experience is a “single point of view” available only to the “experiencer,” not objectively verifiable by another. You can explain sensory perception in a mechanistic way — it is an objective experience of a phenomenon — but the subjective experience it generates — what it feels like — cannot be explained in terms of underlying physical causes. It is not detectable as excitation patterns in the brain. In the language of neuroscience, it has no “neural correlates.” It is purely subjective, unique to the individual. Nagel’s real point is that you can never have the same experience of something as would another individual.

What this means is that no one will ever know what it feels like to be you.

But, you may point out, while it’s stunningly obvious that humans may not have the same experience as bats because of their physical differences, surely they share experiences with others of their kind, particularly with others of similar age and cultural backgrounds.

Tell that to the half of the human race that will never know what childbirth feels like.

But that too is not fair, you say, since it depends on the physical differences between the sexes; only mothers would know what it feels like to push a baby out of a vagina. A man simply wouldn’t.

True, so consider something that is a commonly shared experience: Perception of color.

Two people could consistently agree on what is “red.” You could observe the same electrical signals in their optical apparatus every time they see “red,” a specific frequency on the electromagnetic spectrum. And yet, what one may consistently see as red, the other might — just as consistently — see as blue, though she may call it “red.” (Not that you’d know, since the inner experience of an individual is not accessible to another). The same color “feels” different to another. Since the sensory — objective — experience is measurably the same, what’s different is the subjective experience.

Why should the same objective experience stimulate varying subjective experiences in different individuals? The simple explanation, of course, is “nurture.” Cultural background, upbringing, education, the full weight of a lifetime of memories, or even the pressures of the current moment could certainly influence an individual’s subjective experience of a phenomenon.

But it’s not so simple, of course. It requires another inter-species story to illustrate:

The 5th century Daoist philosopher Zhuangzi reports a conversation with a colleague Huizi as they strolled on the bridge above the Hao river.

“Out swim the minnows, so free and easy,” said Zhuangzi. “This is fish happiness.”

“You are not a fish. Whence do you know that the fish are happy?” challenged Huizi.

“You are not I,” countered Zhuangzi, “How do you know that I don’t know that the fish are happy?”

“Let us grant that not being you, I don’t know about you. You will grant that you are not a fish, and that completes the case that you don’t know that the fish are happy.”

“Let us go back to where we started. When you said, ‘Whence do you know that the fish are happy?’ I knew it from my position on the bridge up above the river Hao.”

By retreating to the physical place from where he detected happiness in fish, Zhuangzi reminds Huizi that in the ordinary day-to-day what matters is the — metaphysical — location of the knower. It is as arbitrary and complex as that. And, just as unchallengeable.

The fundamental problem of human relationships is that we either think we know others’ feelings or that that we expect those feelings to match our own. Neither is ever right. About the only thing we do know about others’ minds — though we may not hear the sound and the fury — is that there are great battles raging within.

Nor should we expect that facts and rational arguments will sway others. As John Locke wrote three hundred years ago in An Essay Concerning Human Understanding: “Earthly minds, like mud walls, resist the strongest batteries: and though perhaps sometimes the force of a clear argument may make some impression, they nevertheless stand firm and keep out the enemy, truth, that would captivate or disturb them.”

It’s a sentiment as true today as it was then. Faced with an immovable object, the most humane of reactions — if one can muster it — is NOT to redouble our efforts. Instead, it is to sheath our swords and drop the battering rams. It is to recognize that our human responsibility is to be kind.

But, equally, after that, to move on.