Ctesias of Knidos was a Greek physician and writer of tales and legends from far-away lands. He is often compared negatively to Herodotus. Herodotus, it is said, wrote histories. Ctesias wrote something else entirely.

He lived sometime in the fifth and fourth centuries. Originally from Knidos, a Greek city in what is now south-western Turkey, he likely practiced medicine as an Asclepiad. At some point in the fifth century he was brought to the Persian Court as a physician, although the circumstances of his move are not clear. Some sources refer to him as physician at the court of Artaxerxes II, a prominent post. If these sources are right, it explains his familiarity with the Persian kingdom. In all, he likely stayed and travelled with the court for 17 years.

When he returned to Knidos at the beginning of the fourth century, he wrote a work called the Indica, the first Greek-language description of the lands, people, animals and plants east of Persia, almost a century before reports would come back from Alexander’s expedition. The book circulated widely. It contained fantastic tales about the strangeness of the lands to the east at the end of the earth—tales Ctesias’ audience would have desired because of how weird and terrifying they were, but whose reality they could (most of the time) safely ignore because of how remote they were. The bestiary he introduced to the Greek world and ultimately to ours includes not just the manticore and the unicorn, but also a bird that can speak in human tongues and a race of half-human, half-dog people called the Cynocephaloi.

I find it especially interesting that his stories are repeated by Aristotle. Aristotle’s History of Animals includes several animals he took from Ctesias’ writings, even though he says Ctesias is not not worth believing (οὐκ ἀξιόπιστος). There is a puzzle here. Aristotle calls Ctesias an untrustworthy source, but at the same time he includes his observations, often without comment and, even more puzzling, often without any indication they are not to be trusted.

The unicorn is one example. Ctesias is clearly Aristotle’s source for his discussion of the unicorn. We know this based on what Aristotle says about the unicorn’s knucklebones and because of the proximity of Aristotle’s unicorn discussion to one about the manticore, which Aristotle says he took from Ctesias. It looks like Aristotle was jotting down notes as he was reading Ctesias’ work.

It is curious, then, that Aristotle does not cite Ctesias as his source for the unicorn passage. Moreover, he gives no indication the report is questionable or not to be trusted. In fact, he doesn’t make it look like a report at all. So the question is: what does the fact that he includes accounts of animals from foreign lands based on the testimony of someone he does not trust mean for Aristotle’s way of collecting facts and doing science?

It’s a question that’s been raised a lot before, and one I think is always worth raising again. What is Aristotle’s attitude to his sources of information about the natural world beyond his experience? And why does he think some stories are worth believing and not others?

(Not-quite) Biogeography

“Animals differ according to place. In certain places, some animals do not exist at all; in some places, they do exist, but they are smaller, or shorter-lived, or they do not thrive. And sometimes a difference like this occurs in neighbouring places, for example, in areas of Miletus that neighbour each other, in one place cicadas exist, in another they do not. There is a river that runs through Cephalenia, where on one side cicadas exist, but on the other they do not. In Boeotia, many moles live around the Orchomenos, but in neighbouring Lebadiake, there aren’t any; even if someone introduces them, they do not wish to make their burrows there. In Ithaca, hares (if someone releases them after introducing them) are not able to live, but are observed dead, turned towards the sea where they had been brought in. In Sicily, there are no horse-ants, while in Cyrene, croaking frogs did not exist before. In all of Libya, there are no wild pigs, no deer, no wild goats. And in India, as Ctesias — who isn’t worth believing — says, there are neither wild nor tame pigs, but massive bloodless [animals] all covered in scales.”

Διαφέρει δὲ τὰ ζῷα καὶ κατὰ τοὺς τόπους· ὥσπερ γὰρ ἔν τισιν ἔνια οὐ γίνεται παντάπασιν, οὕτως ἐν ἐνίοις τόποις γίνεται μὲν ἐλάττω δὲ καὶ ὀλιγοβιώτερα, καὶ οὐκ εὐημερεῖ. Καὶ ἐνίοτε ἐν τοῖς πάρεγγυς τόποις ἡ διαφορὰ γίνεται τῶν τοιούτων, οἷον τῆς Μιλησίας ἐν τόποις γειτνιῶσιν ἀλλήλοις ἔνθα μὲν γίνονται τέττιγες ἔνθα δ' οὐ γίνονται, καὶ ἐν Κεφαληνίᾳ ποταμὸς διείργει, οὗ ἐπὶ τάδε μὲν γίνονται τέττιγες, ἐπ' ἐκεῖνα δ' οὐ γίνονται. Ἐν δὲ Πορδοσελήνῃ ὁδὸς διείργει, ἧς ἐπ' ἐκεῖνα μὲν γαλῆ γίνεται, ἐπὶ θάτερα δ' οὐ γίνεται. καὶ ἐν τῇ Βοιωτίᾳ ἀσπάλακες περὶ μὲν τὸν Ὀρχομενὸν πολλοὶ γίνονται, ἐν δὲ τῇ Λεβαδιακῇ γειτνιώσῃ οὐκ εἰσίν, οὐδ' ἄν τις κομίσῃ, ἐθέλουσιν ὀρύττειν. Ἐν Ἰθάκῃ δ' οἱ δασύποδες, ἐάν τις ἀφῇ κομίσας, οὐ δύνανται ζῆν, ἀλλὰ φαίνονται τεθνεῶτες πρὸς τῇ θαλάττῃ ἐστραμμένοι, ᾗπερ ἂν εἰσαχθῶσιν. Καὶ ἐν μὲν Σικελίᾳ ἱππομύρμηκες οὐκ εἰσίν, ἐν δὲ Κυρήνῃ οἱ φωνοῦντες βάτραχοι πρότερον οὐκ ἦσαν. Ἐν δὲ Λιβύῃ πάσῃ οὔτε σῦς ἄγριός ἐστιν οὔτ' ἔλαφος οὔτ' αἲξ ἄγριος· ἐν δὲ τῇ Ἰνδικῇ, ὡς φησὶ Κτησίας οὐκ ὢν ἀξιόπιστος, οὔτ' ἄγριος οὔτε ἥμερος ὗς, τὰ δ' ἄναιμα καὶ τὰ φολιδωτὰ πάντα μεγάλα.

Aristotle, History of Animals 8.28, 605b22-606a10

Aristotle on Ctesias on the Martichora, or the Manticore

“There is such a thing, if we must trust Ctesias. He says that the beast among the Indians, whose name is ‘martichora,’ has triple-rows of teeth on both sides. In size, he says it is as big as a lion, equally hairy, and having smaller feet. Its face and ears are human-like, its eyes shining blue, its colour like cinnabar. Its tail is similar to that of a land-scorpion, and in it, it has a stinger and it can shoot the spines like arrows. Its cry is like the sound of a shepherd’s-pipe and a war-trumpet at the same time, and it runs as quickly as a deer. It is savage and a man-eater.”

Ἔστι δέ τι, εἰ δεῖ πιστεῦσαι Κτησίᾳ· ἐκεῖνος γὰρ τὸ ἐν Ἰνδοῖς θηρίον, ᾧ ὄνομα εἶναι μαρτιχόραν, τοῦτ' ἔχειν ἐπ' ἀμφότερά φησι τριστοίχους τοὺς ὀδόντας· εἶναι δὲ μέγεθος μὲν ἡλίκον λέοντα καὶ δασὺ ὁμοίως, καὶ πόδας ἔχειν ὁμοίους, πρόσωπον δὲ καὶ ὦτα ἀνθρωποειδές, τὸ δ' ὄμμα γλαυκόν, τὸ δὲ χρῶμα κινναβάρινον, τὴν δὲ κέρκον ὁμοίαν τῇ τοῦ σκορπίου τοῦ χερσαίου, ἐν ᾗ κέντρον ἔχειν καὶ τὰς ἀποφυάδας ἀπακοντίζειν, φθέγγεσθαι δ' ὅμοιον φωνῇ ἅμα σύριγγος καὶ σάλπιγγος, ταχὺ δὲ θεῖν οὐχ ἧττον τῶν ἐλάφων, καὶ εἶναι ἄγριον καὶ ἀνθρωποφάγον.

Aristotle, History of Animals 2.1, 501a24-b1

Aristotle on the Indian Donkey, or the Unicorn

“Some animals have horns, others do not. The majority of those that have horns are naturally cloven-hooved, like the ox, the stag and the goat. We have not observed any single-hooved, two-horned animals. But there are a few animals that are single-horned and single-hooved, like the Indian donkey. The oryx is single-horned and double-hooved. And the Indian donkey is the only single-hooved animal that has a knucklebone.”*

Ἔστι δὲ καὶ τὰ μὲν κερατοφόρα τῶν ζῴων τὰ δ’ ἄκερα. Τὰ μὲν οὖν πλεῖστα τῶν ἐχόντων κέρατα διχαλὰ κατὰ φύσιν ἐστίν, οἷον βοῦς καὶ ἔλαφος καὶ αἴξ· μώνυχον δὲ καὶ δίκερων οὐθὲν ἡμῖν ὦπται. Μονοκέρατα δὲ καὶ μώνυχα ὀλίγα, οἷον ὁ Ἰνδικὸς ὄνος. Μονόκερων δὲ καὶ διχαλὸν ὄρυξ. Καὶ ἀστράγαλον δ’ ὁ Ἰνδικὸς ὄνος ἔχει τῶν μωνύχων μόνον.

Aristotle, History of Animals 2.1, 499b15-20

*Aristotle does not name his source, but Aelian attributes the same claim to Ctesias and I bet Aristotle is getting it from him.

Aelian on the Indian Donkey, or Unicorn

“I have heard that in India there are wild donkeys as big as horses. The rest of their body is white, but the head is very nearly purple and their eyes exude a deep blue colour. They have a horn on their forehead almost a meter long and the lower part of the horn is white, the upper part a deep, dark red, and the middle a dreadful black.

I hear the Indians drink from these colourful-patterned horns — not all of them, but the mightiest of the Indians — and on sections of them they inlay gold as if adorning the arms of a beautiful statue with bracelets. They say the one who has tasted from this horn becomes ignorant and unburdened of incurable diseases. He is not seized by convulsion or what is called the sacred disease nor destroyed by poisons. Even if he had drunk something harmful earlier, he vomits this up and he becomes healthy.

It is believed that the other donkeys across the whole world, both tame and savage, and the other single-hoofed beasts, do not have knucklebones and do not have bile in the liver. But Ctesias says the horned Indian donkey has knucklebones and is not without bile. The knucklebones are said to be black, and if someone grinds them up, they are even like this inside.

They are swifter not only than donkeys, but even horses and deer. They start with a slow pace, but bit by bit they get faster, and to pursue them is, to put it poetically, to chase the uncatchable. When the female gives birth and leads the newborns around, the fathers, who heard with them, also guard the offspring. The donkeys spend their time in most desolate of the plains of India. When the Indian people go on a hunt for them, the [parents] let the tender and still young [offspring] graze behind them, while they fight for them, and go meet the enemy horsemen and strike with their horns. Their horns are so strong. Nothing can withstand a strike from them; instead, they give way and are broken in two, and sometimes they’re shattered and made useless. In the past, they have hit the horses’ ribs, even tearing them open and spilling their vital organs. That is why the horsemen dread getting close to them – the penalty for getting to close is a most pitiable death, and both they and the horses are destroyed. They are able to kick terribly as well. And their bite goes down so deep, that everything they get hold of is ripped off. When full grown, one cannot catch them alive; instead, they are shot with javelins and arrows, and when the Indians have stripped their horn from the corpse, they handle them in the way I mentioned. The meat from the Indian donkey is inedible; the reason: it is naturally very bitter.”

Ὄνους ἀγρίους οὐκ ἐλάττους ἵππων τὰ μεγέθη ἐν Ἰνδοῖς γίνεσθαι πέπυσμαι. καὶ λευκοὺς μὲν τὸ ἄλλο εἶναι σῶμα, τήν γε μὴν κεφαλὴν ἔχειν πορφύρᾳ παραπλησίαν, τοὺς δὲ ὀφθαλμοὺς ἀποστέλλειν κυανοῦ χρόαν. κέρας δὲ ἔχειν ἐπὶ τῷ μετώπῳ ὅσον πήχεως τὸ μέγεθος καὶ ἡμίσεος προσέτι, καὶ τὸ μὲν κάτω μέρος τοῦ κέρατος εἶναι λευκόν, τὸ δὲ ἄνω φοινικοῦν, τό γε μὴν μέσον μέλαν δεινῶς.

ἐκ δὴ τῶνδε τῶν ποικίλων κεράτων πίνειν Ἰνδοὺς ἀκούω, καὶ ταῦτα οὐ πάντας, ἀλλὰ τοὺς τῶν Ἰνδῶν κρατίστους, ἐκ διαστημάτων αὐτοῖς χρυσὸν περιχέαντας, οἱονεὶ ψελίοις τισὶ κοσμήσαντας βραχίονα ὡραῖον ἀγάλματος. καί φασι νόσων ἀφύκτων ἀμαθῆ καὶ ἄπειρον γίνεσθαι τὸν ἀπογευσάμενον ἐκ τοῦδε τοῦ κέρατος· μήτε γὰρ σπασμῷ ληφθῆναι ἂν αὐτὸν μήτε τῇ καλουμένῃ ἱερᾷ νόσῳ, μήτε μὴν διαφθαρῆναι φαρμάκοις. ἐὰν δέ τι καὶ πρότερον ᾖ πεπωκὼς κακόν, ἀνεμεῖν τοῦτο, καὶ ὑγιᾶ γίνεσθαι αὐτόν.

πεπίστευται δὲ τοὺς ἄλλους τοὺς ἀνὰ πᾶσαν τὴν γῆν ὄνους καὶ ἡμέρους καὶ ἀγρίους καὶ τὰ ἄλλα μώνυχα θηρία ἀστραγάλους οὐκ ἔχειν, οὐδὲ μὴν ἐπὶ τῷ ἥπατι χολήν, ὄνους δὲ τοὺς Ἰνδοὺς λέγει Κτησίας τοὺς ἔχοντας τὸ κέρας ἀστραγάλους φορεῖν, καὶ ἀχόλους μὴ εἶναι· λέγονται δὲ οἱ ἀστράγαλοι μέλανες εἶναι, καὶ εἴ τις αὐτοὺς συντρίψειεν, εἶναι τοιοῦτοι καὶ τὰ ἔνδον.

εἰσὶ δὲ καὶ ὤκιστοι οἵδε οὐ μόνον τῶν ὄνων, ἀλλὰ καὶ ἵππων καὶ ἐλάφων: καὶ ὑπάρχονται μὲν ἡσυχῆ τοῦ δρόμου, κατὰ μικρὰ δὲ ἐπιρρώννυνται, καὶ διώκειν ἐκείνους τοῦτο δὴ τὸ ποιητικὸν μεταθεῖν τὰ ἀκίχητά ἐστιν. ὅταν γε μὴν ὁ θῆλυς τέκῃ, καὶ περιάγηται τὰ ἀρτιγενῆ, σύννομοι αὐτοῖς οἱ πατέρες αὐτῶν φυλάττουσι τὰ βρέφη. διατριβαὶ δὲ τοῖς ὄνοις τῶν Ἰνδικῶν πεδίων τὰ ἐρημότατά ἐστιν. ἰόντων δὲ τῶν Ἰνδῶν ἐπὶ τὴν ἄγραν αὐτῶν, τὰ μὲν ἁπαλὰ καὶ ἔτι νεαρὰ ἑαυτῶν νέμεσθαι κατόπιν ἐῶσιν, αὐτοὶ δὲ ὑπερμαχοῦσι, καὶ ἴασι τοῖς ἱππεῦσιν ὁμόσε, καὶ τοῖς κέρασι παίουσι. τοσαύτη δὲ ἄρα ἡ ἰσχὺς ἡ τῶνδέ ἐστιν. οὐδὲν ἀντέχει αὐτοῖς παιόμενον, ἀλλὰ εἴκει καὶ διακόπτεται καὶ ἐὰν τύχῃ κατατέθλασται καὶ ἀχρεῖόν ἐστιν. ἤδη δὲ καὶ ἵππων πλευραῖς ἐμπεσόντες διέσχισαν καὶ τὰ σπλάγχνα ἐξέχεαν. ἔνθεν τοι καὶ ὀρρωδοῦσιν αὐτοῖς πλησιάζειν οἱ ἱππεῖς: τὸ γάρ τοι τίμημα τοῦ γενέσθαι πλησίον θάνατός ἐστιν οἴκτιστος αὐτοῖς, καὶ ἀπόλλυνται καὶ αὐτοὶ καὶ οἱ ἵπποι. δεινοὶ δέ εἰσι καὶ λακτίσαι. δήγματα δὲ ἄρα ἐς τοσοῦτον καθικνεῖται αὐτῶν, ὡς ἀποσπᾶν τὸ περιληφθὲν πᾶν. ζῶντα μὲν οὖν τέλειον οὐκ ἂν λάβοις, βάλλονται δὲ ἀκοντίοις καὶ οἰστοῖς, καὶ τὰ κέρατα ἐξ αὐτῶν Ἰνδοὶ νεκρῶν σκυλεύσαντες ὡς εἶπον περιέπουσιν. ὄνων δὲ Ἰνδῶν ἄβρωτόν ἐστι τὸ κρέας: τὸ δὲ αἴτιον, πέφυκεν εἶναι πικρότατον.

Aelian, On the Nature of Animals 4.52