by Sam Kean
On top of all this, the biological theory of plausibility also suffers from a graver problem: its predictive powers are faulty. By its logic, many creatures that we find highly believable should instead rank near the bottom of the list. Angels, for instance, are physiologically unlikely: in addition to being able to fly (fine for birds, unheard of in hominids), they manifest a particularly extreme version of the limb problem, since, per various sources, they have not just two but in some cases hundreds of wings. Demons present the same basic difficulties, as do fairies, and ghosts defy pretty much every biological principle: among other problems, they have no substance, require no sustenance, and do not decay or die. Yet given that seven out of ten Americans believe in angels, six out of ten believe in demons, and almost half believe in ghosts, it seems safe to assume that, on the scale of plausibility, such creatures outrank giants and unicorns.
So much for biology as the basis of our unified theory. But we can resolve at least some of these problems by modifying our hypothesis slightly. Perhaps we don’t care how much supernatural creatures resemble the animal kingdom in general; perhaps we only care how much they resemble us. This mirror theory of plausibility would still account for the high ranking of yetis, which, aside from not existing, are not so different from Homo sapiens. (Back in 2004, when scientists discovered an extinct species of an unusually small hominid on an island in Indonesia, a senior editor at Nature took the occasion to speculate that stories about yetis might reflect an extinct Himalayan species on the other end of the size spectrum.) The mirror theory would also explain the perceived plausibility of angels and demons, which, as presented in myth and literature, resemble exaggerated humans in our best and worst incarnations: moral giants and moral elves. And it would explain why vampires and werewolves, which should rank low on the list, what with the impossibility of radical metamorphosis, generally rank quite high. When they are not busy sprouting wings and fur, after all, such creatures look nearly indistinguishable from us.
On the other hand, this theory leads us quickly into ontological problems: are we humans more like mermaids, or more like ghosts? Worse, like the biological theory of plausibility, it fails to account for some of our intuitions about supernatural beings. Why, for example, would a centaur, which is 50 percent human, strike us as less plausible than a unicorn, which is 0 percent human? And what are we to make of natural-born humans who are able to do supernatural things, à la Shakespeare’s Prospero, Hermione Granger, or that menace of Camelot Morgan le Fay?
This last category of being opens up a whole new can of worms. Magical creatures exist in a universe of magical powers, which themselves range wildly in probability and are not evenly distributed among the population. To understand our intuitions about plausibility, then, we need to look beyond entities to actions. For supernatural creatures, as for the rest of us, it might be that what matters most is not what we are but what we do.
What do supernatural creatures do? In many cases, not much. Somewhat strangely, not every magical being has magical powers. Some, like Santa Claus and the tooth fairy, mostly just have chores. Others merely hang around looking unusual; the yeti and Nessie just lurk; the Leviathan lurks, too, largerly; the record is mixed on giants, which in some accounts live on clouds but in most are just enormous and crabby. Wraiths only scare people, centaurs only awe people, and unicorns, aside from some healing properties in their horns, akin to the antibiotics in frog skin, only attract virgins—which, power-wise, puts them at the same level as boy bands. For these and many other supernatural creatures, their supernaturalness inheres chiefly in the fact (or the non-fact) of their existence.
Others, however, can do flatly impossible things. Fairies, by most accounts, can turn invisible, tell the future, and shape-shift. Ghosts can shrink, expand, time-travel, and walk through walls. Vampires can command the dead, summon storms, control lesser animals like bats and wolves, and—barring certain interventions with stakes or sunlight—live forever. Various other entities can, through their own powers or via potions, amulets, and spells, likewise achieve the unachievable: levitate, teleport, transmogrify, read minds, talk to animals, and, by occult means, charm, confuse, possess, haunt, hex, heal, or kill.
Like supernatural creatures, such powers can be ranked in terms of plausibility. Which seems more likely to work: Harry Potter’s apparating ability or Obi-Wan Kenobi’s Jedi mind trick? If you ask me, it’s obviously the mind trick, with its real-life analogies of charisma and hypnosis, not to mention its failure to defy any major laws of physics. On the other hand, apparating—vanishing from one place and appearing in another—strikes me as more plausible than time travel, possibly because we have many ways to move through space but only one way to move through time.
You can play this game forever, with any given set of magical powers. Controlling the elements, for instance, seems considerably harder than controlling an animal (unless, perhaps, it is a cat)—but, if you are going to try to control the elements, summoning a breeze seems easier than turning night to day. If you’re going to work magic on your own body, becoming invisible seems more plausible than transmogrifying, perhaps because of the abundance of everyday ways to conceal ourselves. Yet, if transmogrification is going to occur, I’d wager that it is easier to turn oneself into a wolf than one’s enemy into a toad.
As it happens, intuitions like these are broadly shared—a fact we know because, speaking of implausible things, two cognitive scientists at the Massachusetts Institute of Technology have shown it. Normally, Tomer Ullman studies our commonsense beliefs about physics and psychology, while his colleague John McCoy studies judgment and decision-making. Together, however, they figured that looking at how we reason about supernatural powers might shed light on how we reason about the real world. To that end, in 2015 they asked 200 people, ranging in age from eighteen to eighty-three, to rank 10 magic spells in order of difficulty. Since amphibians in magic have roughly the same status as rodents in science, all the spells featured things a sorcerer could do to a frog: conjure it into existence, conjure it out of existence, teleport it, levitate it, change its color, double its size, turn it into two frogs, turn it into a mouse, turn it to stone, and turn it invisible.
The results help explain why I am dubious about apparating. Overall, the subjects felt that spells were more difficult when they violated “more fundamental principles of intuitive physics.” What makes a principle of physics fundamental, in this case, is how early in our cognitive development we acquire it. For instance, we are born with an understanding of object permanence, and the two spells that violated it, by conjuring a frog into or out of existence, were ranked the most difficult. Similarly, we learn in infancy that objects have what developmental psychologists call “kind-identity”—they stay themselves—which may explain why the next-hardest spell involved turning a frog into a mouse. The two easiest spells, by comparison, entailed changing a frog’s color and levitating it, results that reflect our awareness that both color and location are transient rather than fixed features of the physical world.
To further plumb our intuitions about supernatural powers, McCoy and Ullman ran a second study, which asked the same questions but changed one of two things: either the target of the spell (Is it harder to conjure a frog or a cow?) or the extent of its power (Is it harder to levitate a frog 1 foot or 100 feet?). Resoundingly: a cow; 100 feet. These findings are striking, since levitating something 99 extra feet does not violate any additional principles of physics. Nor does conjuring a cow instead of a frog. So why would those variants seem more challenging?
Happily, two other cognitive scientists, Andrew Shtulman and Caitlin Morgan, of Occidental College, have addressed that question. (Full disclosure: my sister, a cognitive scientist at MIT, was Shtulman’s postdoctoral adviser and has worked with McCoy and Ullman.) Last year, Shtulman and Morgan gave people pairs of magic spells and asked them to determine which one in each pair was more difficult. In every pair, both spells violated the same fundamental principle of
physics, biology, or psychology, but each varied in how much it violated a secondary one. For instance, physics dictates that you can’t walk through anything solid, no matter what it’s made of, but also that materials differ with respect to properties like density and hardness. So which seems more difficult: walking through a wall made of stone or a wall made of wood?
Overwhelmingly, the subjects chose stone. They also determined that it would be harder to levitate a bowling ball than a basketball, and harder to grow an eye than a toe. Since levitation is categorically impossible, it shouldn’t matter that heavier objects, like bowling balls and cows, are harder to lift. But, as Aristotle understood, it does. According to Shtulman and Morgan, that’s because our understanding of causation—our sense of which things make other things happen—is not a series of separate if-then statements but a vast interconnected web, which continues to govern our intuitions even when one particular strand snaps. “Severing one link in a causal network,” they write, “still leaves the rest of the network intact.” And the more links you sever, the more powerful—or, put differently, the less probable—your magic seems.
Perhaps, then, the solution we seek is mathematical: tally up all the fundamental principles violated by a supernatural creature and its powers and—voilà, we’ll know where it stands in the hierarchy of likelihood. Call this the parsimony theory of plausibility: the fewer laws something violates, the more credible it will seem. The yeti, for instance, doesn’t really violate any natural laws at all. Vampires, by contrast, violate everything from the fact that things of substance cast shadows to Meteorology 101.
This parsimony theory is simple, elegant, and, unfortunately, wrong. If it were correct, we’d all find gnomes, whose only distinguishing characteristics are diminutiveness, avarice, and a preference for living underground, considerably more plausible than ghosts. Yet ghosts, despite their utter disregard for biology and physics, persist in seeming highly believable. Part of that might be explained by our existential condition: most of us feel that we have a core self, separate and separable from our body, and most of us find it hard to accept that we will someday cease to exist.
Part of it, however, might be explained by one final theory of supernatural plausibility. Consider a defense that my sister once mounted on behalf of the likelihood of fairies. Small impossible things, she contended, are more believable than large impossible things, because they could more easily exist without us noticing them. That argument isn’t based on our beliefs about physics or biology; it’s based on epistemology. From infancy on, we are extraordinarily sensitive to patterns of evidence (in fact, that’s how we acquire many of our beliefs about physics and biology), so it seems reasonable to think that evidence also determines our judgments about fantastical beings.
Of course, it also seems unreasonable to think that, since it’s unclear how we would find evidence for the existence of nonexistent creatures. In its absence, we can make do, as my sister did, with a good reason for why we haven’t found it, a strategy that lends plausibility not only to fairies in their tininess but also to ghosts and other creatures capable of vanishing. (It also gives us a reason, finally, to object to the yeti: if it existed, we should have found proof by now.)
Alternatively, we can accept attestation as a form of evidence—which, across domains, we do all the time, since many of our convictions about the world concern things we ourselves will never observe. Our sensitivity to attestation explains why culture has such a potent influence on our intuitions about the supernatural, which wouldn’t be the case if those intuitions were governed chiefly by biology or physics. It is why one community is more likely to believe in fairies and another in zombies, and why, with churches peddling a more palliative version of Christianity, demons have declined in plausibility vis-à-vis angels. And it is why, if you’re European American, you’re more likely to believe in a vampire than in the coffin-dwelling, night-roaming, life-force-sucking Chinese jiangshi, even though, on the basis of their characteristics, there is not, so to speak, a lot of daylight between them.
Patterns of evidence, a grasp of biology, theories of physics: as it turns out, we need all of these to account for our intuitions about supernatural beings, just as we need all of them to explain any other complex cultural phenomenon, from a tennis match to a bar fight to a bluegrass band. That might seem like a lot of intellectual firepower for parsing the distinctions between fairies and mermaids, but the ability to think about nonexistent things isn’t just handy for playing parlor games on Halloween. It is utterly fundamental to who we are. Studying that ability helps us learn about ourselves; exercising it helps us learn about the world. A three-year-old talking about an imaginary friend can illuminate the workings of the human mind. A thirty-year-old conducting a thought experiment about twins, one of whom is launched into space at birth and one of whom remains behind, can illuminate the workings of the universe. As for those of us who are no longer toddlers and will never be Einstein: we use our ability to think about things that aren’t real all the time, in ways both everyday and momentous. It is what we are doing when we watch movies, write novels, weigh two different job offers, consider whether to have children.
As that last example suggests, perhaps the most extraordinary thing about this ability is that we can use it to nudge the impossible into the realm of the real. We stare at the sky, watch a seagull bob on a thermal, build wax wings and then fixed wings and then Apollo XI. We dream of black presidents and female scientists; we dream, still, of self-driving cars, a cure for cancer, peace in the Middle East. These last things are interestingly like dragons and also interestingly unlike dragons, in ways that suggest that we may be wise, after all, to treat impossibility as something other than an absolute condition. Alone among all the creatures in the world, we can think about fantastical things and, at least some of the time, bring them into being.
Yet, in the end, what’s most remarkable is not that our fantasies contain so much reality; it is that our reality contains so much fantasy. Most of us understand that our perceptual systems, far from passively reflecting the world around us, actively sort, select, distort, ignore, and alter a huge amount of information in order to construct reality as we experience it. But reality as we experience it also departs from actual reality in deeper ways. In actual reality, space and time are inseparable, and neither one behaves anything like the way we perceive it; nor does light, and nor does gravity, and, in all likelihood, nor does consciousness. Yet all the while we go on experiencing space like a map we can walk on, time like a conveyor belt we travel on, ourselves as brimming with agency, our lives as mattering urgently.
That world, the one we inhabit every day of our lives, is a yeti—a fantastical thing constructed out of bits and pieces of reality plus the magic wand of the mind. If we could hand it over to some superior being for consideration, it might not even rank very high on the scale of plausibility. Then again, plausibility itself might not rank very high on the scale of qualities we prize. Better, perhaps, to know that what we feel in our happiest moments has some truth to it: life is magical.
Contributors’ Notes
Ross Andersen is a senior editor at The Atlantic.
Rebecca Boyle is an award-winning freelance journalist who focuses on how things work and the ways humans try to understand the universe. Her magazine writing covers astronomy and physics, geoscience and climate change, and the history of science. She is a contributing writer for The Atlantic, and her work regularly appears in FiveThirtyEight, New Scientist, Quanta, and many other publications for adults and kids. Rebecca grew up in Denver and dreams of the pristine night skies over the Rocky Mountains. She lives in St. Louis with her family.
Sophie Brickman is a writer and editor based in New York City. Her work has been published in The New Yorker, the New York Times, and the San Francisco Chronicle, among other places.
Kenneth Brower is the son of the pioneering environmentalist David Brower. His first memories are of the Sierra Nevada and the wild coun
try of the American West. He is a freelance writer and the author of many books and magazine articles on the environment and natural history. His work has taken him to all the continents. He lives in Berkeley, California.
Jacqueline Detwiler is a senior editor at Popular Mechanics. She has also written for Wired, Esquire.com, Entrepreneur, and other publications. She holds an M.A. in psychology and neuroscience from Duke University and is the host of Popular Mechanics’ podcast, The Most Useful Podcast Ever.
Ceridwen Dovey regularly contributes nonfiction to newyorker.com, and is the author of the novels Blood Kin and In the Garden of the Fugitives and the short-story collection Only the Animals. She lives in Sydney, Australia.
Susannah Felts is a writer, editor, and cofounder/co-director of The Porch, a literary arts organization in Nashville, Tennessee. She is the author of a novel, This Will Go Down on Your Permanent Record, and her essays and fiction have appeared in publications such as Guernica, Longreads, Catapult, Oxford American, the Sun, Hobart, Smokelong Quarterly, and others. She’s at work on a novel.
Douglas Fox (www.douglasfox.org) is a freelance journalist who writes extensively on Earth, the Antarctic, and polar sciences. His stories have appeared in Scientific American, National Geographic, Esquire, Virginia Quarterly Review, High Country News, Discover, Nature, Slate, the Christian Science Monitor, and other publications. Stories by Doug have garnered awards from the American Society of Journalists and Authors (2011), the National Association of Science Writers (2013), the American Geophysical Union (2015), the Society of Environmental Journalists (2016), and the American Association for the Advancement of Science (2009, 2017). Doug is a contributing author to The Science Writers’ Handbook.
