Half our days we pass in the shadow of the earth; and the brother of death exacteth a third part of our lives. A good part of our sleep is peered out with visions and fantastical objects, wherein we are confessedly deceived. The day supplieth us with truths; the night with fictions and falsehoods, which uncomfortably divide the natural account of our beings. And therefore, having passed the day in sober labours and rational enquiries of truth, we are fain to betake ourselves unto such a state of being, wherein the soberest heads have acted all the monstrosities of melancholy, and which unto open eyes are no better than folly and madness.

So writes the English doctor, essayist, and human curiosity Sir Thomas Browne (1605-82) in a short essay “On Dreams.” Browne’s division of daylight rational inquiry from nighttime fictions and falsehoods is a good place to begin an inquiry into the existence of unicorns, not least because Browne himself investigated the issue in his Pseudoxia Epidemica or Enquiries into very many received tenents  and commonly presumed truths (1672). Browne’s target is “vulgar” or popular errors–folk beliefs that persist despite his age’s burgeoning sense of reason. How, he wonders, are people so “ready with open armes to receive the encroachments of Error”?

Among those persistent errors regarding the natural world that peeved Sir Thomas are the beliefs that pigeons have no gall, that a bear shapes her cubs at birth like clay, that an ostrich will digest iron, that moles have no eyes. Browne likewise takes aim at the unicorn–a creature whose inclusion in the most comprehensive encyclopedia of animals of the time, Edward Topsell’s History of Four-Footed Beasts (1658), perhaps owes to the fact that that book was a translation of German naturalist Conrad Gesner’s Historiae Animalium (1551-58) written over a hundred years earlier. By Browne’s time, it’s more than likely he was dispelling the dreams of an age that had already awaken.

Edward Topsell, "Of the Unicorn." History of Four-Footed Beasts and Serpents. 1658.

Edward Topsell, “Of the Unicorn.” History of Four-Footed Beasts and Serpents. 1658.

But maybe this assessment, like Browne’s, is too hasty. Are we so sure unicorns don’t exist? This is the question I posed to my Science and Literature class in a recent lecture and which I want to explore here over a series of posts. I’ll eventually get around to answering the question, but first it’s helpful–and fun–to figure out exactly what a unicorn is before deciding that it never was.

I was talking about the history of the unicorns in a college class because it turns out that the unicorn is a great case study in the history of science. If you understand how the unicorn managed to make it all the way to the 17th century, you can understand a bit about how we come to know and understand the natural world.

For most of us, the unicorn is a childhood fantasy character–a cartoon adornment of school lunchboxes and Trapperkeepers™. I’m embarrassed to admit that as a young would-be artist, I drew a lot of unicorns, and they were all the same: magnificent white horse-like beasts with glowing horns that acted like lightning rods for rainbows. My unicorns were mostly the barely sublimated expression of pre-adolescent sexual desire for the lithe, long-haired ladies of my 5th and 6th-grade classes, to whom I freely gave them out. (Unless of course they were an excuse for a boy to draw rainbows….) They looked more or less like this, but with more rainbow:

Unicorn drawing

More recently I’ve been hearing the word “unicorn” as applied to something whose improbability is an index of its desirability, as in: “I need a shuttle service that gets me to LAX in under 35 minutes.” “You could just ride a unicorn.” This is actually a much older usage: a 1905 Dictionary of Slang and Colloquial English defines unicorn as “two men and a woman (or vice versa) working together.” Haha.

But the unicorn as an object of scientific investigation is a lot older still, and weirder. Probably the first descriptive account of it is from a 4th-century BCE Greek doctor and explorer named Ctesias of Cnidus, who is reported to have seen a unicorn during a trip to India, which he recorded in his work, the Indika. (That this work shares its name with a species of marijuana seems appropriate.)

At this time, India was a stand-in for all that was fantastic in the minds of ancient Greeks, just as the Americas would be two thousand years later for Renaissance Europeans. It was the edge of the known world and represented the limits of Greek knowledge. As such, it was, like Browne’s dreams, somewhere between the daylight of wakeful reason and the nighttime of fretful visions: things on the margins are either too large or too small, the feverish hallucinations of a culture’s ignorance and craving for curiosities. Among other things, Ctesias described giant roosters and men that lived impossibly long lives. The sun appears ten times larger in India than in Greece and the reeds grow to the height of ships’ masts. Conversely pygmies live there, too, who keep sheep the size of lambs and oxen the size of rams. Ctesias was the first to describe the Cynocephaloi, or dog-headed men, and the martichora, a creature with the face of a human, the body of a lion, and the tail of a scorpion. Such creatures would still haunt the Medieval imagination much later.

Ctesias also describes a “wild ass” the size of a horse, with a

white body, crimson head, and deep blues eyes. They have a horn in the middle of their brow one and a half cubits in length [or 68.58 cm or 27 in]. The bottom part of the horn for as much as two palms towards the brow  is bright white. The tip of the horn is sharp and deep vermillion in colour while  the rest in the middle is black. They say whoever drinks from the horn (which they fashion into cups) is immune to seizures and the holy sickness and suffers no effects from poison…. [Ctesias] also says that other asses, both tame and wild, and the other solid-hoofed animals have no astragalos [or astragalus, the ball-joint of the ankle] or bile in the liver. However, these creatures do have an astragalos and bile in the liver. The astragalos, which is similar in size and shape to that of an ox, is the most beautiful I have ever seen. It is as heavy as lead and the color of cinnabar even at its deepest points. This animal is extremely swift  and strong and neither horse  nor any other animal can overtake it in pursuit. It begins running slowly, but the longer it runs, the more speed it picks up as it exerts itself brilliantly. Usually this animal cannot be hunted, but when they bring their young to pasture and are surrounded by many men on horseback, they choose not to flee and abandon their colts; rather, they fight both with their horn and by kicking and biting. They kill many many horses and men, but they are taken down by the bow or javelin, as one could never capture them alive. Their flesh is inedible on account of its bitterness, but they are hunted for their horns and astragaloi.” 1

Thus, the unicorn. A single paragraph of description of an ass putatively written 2500 years ago. I say “putatively” because the text of the Indika was lost and so despite this “original” description, the unicorn as a species has no origin: the authority on which it’s based survives only as a series of quotations–a waking dream reported by a sojourner to a twilight land of wonders who may or may not have set foot there.

Ctesias’s authority, unlike that of the later, unimpeachable Aristotle, was not held in high esteem, probably because of his penchant for reporting wonders like the Cynocephaloi or the martichora. But as Ctesias translator Andrew Nichols argues, it’s possible that these wonders were of interest to later writers who preserved them and who passed over more mundane details that might have established Ctesias as an authoritative observer. For when Ctesias’s descriptions align with reality, they are quite accurate: later works refer to his description of the bittakos. a bird the size of a falcon with a red face and blue body and which can converse in Indian as well as Greek. This would have seemed wondrous indeed to a culture unfamiliar with parrots.

Despite the unbelievability of his accounts, they survive because they continued to circulate as citations among other historians, natural and otherwise. Even Aristotle, the ultimate authority of antiquity and who among all the early naturalists was probably the only one to insist on making actual observations of the natural world, recorded Ctesias’s account of the single-horned beast in his Historia Animalia, and did so without revealing any suspicion:

some animals are horned, some hornless. Most of the horned ones are cloven-hoofed, e.g., the ox, the deer, and the goat; we have no no solid-hoofed animal with a pair of horns. But a few, e.g., the Indian ass, have a single horn and cloven hooves. The only solid-hoofed animal with a huckle-bone [i.e., the astragalus or ankle-joint] is the Indian ass. 2

Into the Common Era, Roman encyclopedists like Pliny in the 1st-century and Aelian in the 2nd also kept unicorns in circulation. Together, these historians described a species that would live thousands of years in the European imagination before going extinct, a victim of the Enlightenment insistence on empirical evidence and falsification, of which Browne’s Pseudoxia is among the first examples.

If anything, Ctesias and his unicorn belong to a history of error more than to science. Ctesias probably never ventured beyond the Indus Valley in the north of India and thus never even knew of a subcontinent, and so his title itself is geographically misleading 3: it refers more to an idea, a fantasy, than an actual place. In addition, he was probably reporting the oral history of travelers from India rather than making observations first-hand. What’s more, his original record of these indirect accounts was eventually lost, and so even that evidence, such as it was, has little merit. And finally, what little evidence that remains has been distorted by the desire for curiosities of later writers who recorded–cited–these errors in their own too credulous attempts to catalog the natural world in encyclopedias that demonstrate less interested than we do in distinguishing between things reported and things real.

This would seem to be the end of the story: unicorns don’t exist. Except for a couple of things. First, including such an account in one’s own encyclopedia of the known world, however unreliable, makes good sense, doesn’t it? Someone said they saw something. They had no falsifying evidence, so it could be true. Why not include it for someone to disprove later, just in case? Isn’t that kind of curiosity and credulity part of the scientific spirit, if not method? Certainly the world held wonders yet undiscovered and travelers were bringing back more all the time.

But second, more than the spirit of inquiry, there is method: Not only does Ctesias’s account reveal that someone somewhere saw something, those details seem so tantalizingly specific that they cannot be ignored, not even by Aristotle. Such specificity is hard to discount. Something somewhere gave someone the vivid impression of a one-horned animal that exhibited some physical characters (color of coat; number, length, and color of horn; relative size; shape of hoof and ankle-bones; absence of bile; speed), which demonstrated some definite ethological characters (they defend their young aggressively; they attack with horn and teeth), which haunted a particular geography (roughly India; possibly the Himalayan plains; probably Tibet), and which possessed some cultural value in the form of commodities (the horn for drinking; the astragloi for gambling, as dice; the flesh for eating);and which lent itself to amusing stories (they kill many men and horses and cannot be taken alive).

Indeed, early accounts of the unicorn possess all the hallmarks of what we now know as natural history–the observation and description of life. Except for one thing: the creature discovered and described does not appear to have existed. If not the unicorn, what, then, did Ctesias discover? Is it possible to discover something that doesn’t exist? If Ctesias did not discover the unicorn (which at this point I am unwilling to admit), what he did was reveal the possibility of one, which may have been even more wondrous indeed. These are the subjects of my next post!


  1.  Ctesias on India and Fragments of his Minor Works. Trans. Andrew Nichols. London: Bristol Classics, 2011. 56
  2. Aristotle, Historia Animalia. Book II. Trans. A. L.. Peck. Harvard University Press, 1970. II.1.
  3. See Chris Lavers, The Natural History of Unicorns (Harper Perennial, 2010), who helps pinpoint some of the historical details of early accounts of the unicorn.