Maybe because it’s Winter Solstice, the darkest and hence most spiritual time of year, I’ve been thinking about souls. By soul I mean essence, what makes you uniquely you and me uniquely me.

From one point of view, souls cannot possibly exist. To be human is to shape-shift, shedding one identity after another. Think of all the transitions we go through on the way from infancy to adulthood. In my mid-20s I was a house painter living in Denver. Twenty years later I was a full-time staff writer for Scientific American, a married father of two living in the woods north of New York City. Today I am divorced, and I live and teach at a school in Hoboken, New Jersey.

We undergo micro-changes, too. In the course of a single day I slip through many moods, from glum to giddy. Neuroscientists point out that links between our brain cells are constantly weakening, strengthening, dissolving, re-forming. Constantly! Right now, as you read these words, your brain is re-wiring itself, re-inventing itself. Scientists call this property neuroplasticity.

When I read about neuroplasticity, I envision my brain as a mass of squirming worms. No wonder many authorities on the mind--philosophers, cognitive scientists, Buddhists--suggest that the self is an illusion. Buddhists have coined a term for the self’s non-existence: anatta.

And yet. Something within us endures in spite of our never-ending changes. In his book The Perpetual Now: A Story of Amnesia, Memory and Love, science journalist Michael Lemonick tells the story of Lonni Sue, a commercial artist who suffered brain damage as a result of a viral infection. She was left unable to recall her past or to form new memories. Hence the book’s title.

Lemonick assumed that Lonni Sue, when she lost her memories, lost her self. Because what are we but our memories? But once he got to know Lonni Sue, as well as people who knew her before and after her injury, Lemonick discovered that her self had not been destroyed. She was still cheerful in a way that made people around her feel better, and she was still creative and playful, drawing pictures crammed with visual and verbal puns.

Someone dear to me recently suffered a stroke that made it hard for him to understand and be understood by others. But he is still the same indomitable, cheerful, funny man I have always known. There is no essence and there is.

Self seems too bland to describe this mysterious, enduring, one-per-person essence. That’s why I like soul. I don’t think souls are exclusive to humans. Suzie, my ex-wife, rehabilitated wild birds. People would bring her baby birds that had fallen out of their nests, or adults that had run into a window, been clawed by a cat or wounded by a hunter.

Suzie specialized in raptors, such as hawks and owls, but she also took care of sparrows, crows, geese, herons, goldfinches, starlings, you name it. Suzie raised the babies, and nursed the adults back to health. If all went well, she released them into the wild.

We lived with some of these birds for months and got to know them pretty well. And the better we knew the birds, the more we could discern differences between them. Each species had its own personality, and so did each individual bird. This teenage blue jay would be reserved, that one bold, this sparrow shy and that one aggressive. We lived one summer with a crow named George who definitely had a mischievous, sweet soul.

Value, you might argue, is proportional to individuality. We should cherish what is unique, one of a kind. If each bird has her own personality, her own soul, how horrible is the genocide that we commit against them, directly and indirectly! This problem might not bother you if you think souls are immortal and hence that all organisms live happily forever and ever in heaven. But what if you believe, as I do, that when we die that’s it?

I recently attended a conference, “Animal Consciousness,” at which philosophers and scientists debated whether trout, octopuses, bees, jellyfish and other non-human creatures are conscious and hence deserving of ethical consideration. Our tendency is to think that the more unlike us creatures are, the less likely they are to be conscious and hence deserving of ethical consideration. According to his criterion, we should be able to crush a jumping spider without feeling bad about it, because it’s just a tiny machine.

But what if the jumping spider is conscious and has a unique personality? A soul? Implausible, you say. But one speaker at “Animal Consciousness” argued that bees are so complicated that they are probably conscious. Science journalist Carl Zimmer, in his 2008 book Microcosm, notes that if you put genetically identical E. coli in identical environments--a dish of nutrients, for example—they do not always behave identically. E. coli!

Our world, I suspect, teems with an infinitude of souls, human and inhuman, springing into being and vanishing moment by moment. How marvelous that is, and how terrible. These, at any rate, are my thoughts on the darkest day of the year.

Further Reading:

Seeing the Miracle of Existence in the Darkest of Times

Do Fish Suffer?

Crows Aren’t Just Smart, They’re Also Jokers

Jellyfish, Sexbots and the Solipsism Problem

What Is Philosophy’s Point?

CatCam Probes Philosophical Puzzle: What Is It Like to Be a Cat?

Is Consciousness Real?

The Mind–Body Problem, Scientific Regress and "Woo"

Is Scientific Materialism "Almost Certainly False"?

Dispatch from the Desert of Consciousness Research, Part 1

Can Integrated Information Theory Explain Consciousness?

Why information can't be the basis of reality

How Would AI Cover an AI Conference?

World's Smartest Physicist Thinks Science Can't Crack Consciousness

Christof Koch on Free Will, the Singularity and the Quest to Crack Consciousness

David Chalmers Thinks the Hard Problem Is Really Hard

Meta-post: Horgan Posts on Brain and Mind Science.