Gaius Julius Caesar Augustus Germanicus - Caligula

© Copyright Peter Crawford 2016


Caligula was the popular nickname of Gaius Julius Caesar Augustus Germanicus (31 August AD 12 – 24 January AD 41), Roman emperor (AD 37–41).
Born Gaius Julius Caesar (not to be confused with Gaius Julius Caesar who was assassinated in 44 BC), Caligula was a member of the Julio-Claudian dynasty.
Caligula's father Germanicus, the nephew and adopted son of Emperor Tiberius, was a successful general, and one of Rome's most beloved public figures.
The young Gaius earned the nickname "Caligula" (meaning "little soldier's boot", the diminutive form of caliga, hob-nailed military boot) from his father's soldiers while accompanying him during his campaigns in Germania.
When Germanicus died at Antioch in AD 19, his wife Agrippina the Elder returned with her six children to Rome, where she became entangled in a bitter feud with Tiberius.
The conflict eventually led to the destruction of her family, with Caligula as the sole male survivor. 
Untouched by the deadly intrigues, Caligula accepted the invitation to join the Emperor in AD 31 on the island of Capri, where Tiberius had withdrawn five years earlier.
With the death of Tiberius in AD 37, Caligula succeeded his grand uncle and adoptive grandfather as emperor.
There are few surviving sources about the reign of Emperor Caligula, although he is described as a noble and moderate ruler during the first six months of his reign.
After this, the sources focus upon his cruelty, sadism, extravagance, and sexual perversity,.
While the reliability of these sources is questionable, it is known that during his brief reign, Caligula worked to increase the unconstrained personal power of the emperor, as opposed to countervailing powers within the principate.
He directed much of his attention to ambitious construction projects, and luxurious dwellings for himself, and initiated the construction of two aqueducts in Rome: the Aqua Claudia and the Anio Novus.
During his reign, the empire annexed the Kingdom of Mauretania as a province.
In early AD 41, Caligula was assassinated, aged 29, as a result of a conspiracy by officers of the Praetorian Guard, senators, and courtiers.
The conspirators' attempt to use the opportunity to restore the Roman Republic was thwarted: on the day of the assassination of Caligula, the Praetorian Guard declared Caligula's uncle, Claudius, the next Roman emperor.


Gaius Julius Caesar (named in honor of his famous relative) was born in Antium on 31 August 12 AD, the third of six surviving children born to Germanicus and his second cousin Agrippina the Elder.
Gaius had two older brothers, Nero and Drusus, as well as three younger sisters, Agrippina the Younger, Julia Drusilla and Julia Livilla.
He was also a nephew of Claudius (Tiberius Claudius Nero), Germanicus' younger brother and future emperor.
Agrippina the Elder was the daughter of Marcus Vipsanius Agrippa and Julia the Elder.
She was a granddaughter of Augustus and Scribonia on her mother's side.
Through Agrippina, Augustus was the maternal great-grandfather of Gaius.
As a boy of just two or three, Gaius accompanied his father, Germanicus, on campaigns in the north of Germania.
The soldiers were amused that Gaius was dressed in a miniature soldier's outfit, including boots and armour.
He was soon given his nickname Caligula, meaning "little (soldier's) boot" in Latin, after the small boots he wore.
Gaius, though, reportedly grew to dislike this nickname.
After the death of his father, Caligula lived with his mother until her relations with Tiberius deteriorated.
Tiberius would not allow Agrippina to remarry for fear her husband would be a rival.
Agrippina and Caligula's brother, Nero, were banished in 29 AD on charges of treason.
The adolescent Caligula was then sent to live with his redoubtable great-grandmother (and Tiberius's mother) Livia.
After her death, he was sent to live with his grandmother Antonia.
In 30 AD, his brother, Drusus Caesar, was imprisoned on charges of treason and his brother Nero died in exile from either starvation or suicide.
After the banishment of his mother and brothers, Caligula and his sisters were nothing more than prisoners of Tiberius under the close watch of soldiers.
In 31 AD, Caligula was remanded to the personal care of Tiberius on Capri, where he lived for six years.
To the surprise of many, Caligula was spared by Tiberius.
According to historians, Caligula was an excellent natural actor and, recognizing danger, hid all his resentment towards Tiberius.
An observer said of Caligula, "Never was there a better servant or a worse master !"
Caligula claimed to have planned to kill Tiberius with a dagger in order to avenge his mother and brother: however, having brought the weapon into Tiberius's bedroom he did not kill the Emperor but instead threw the dagger down on the floor.
In 33 AD, Tiberius gave Caligula an honorary Quaestorship, a position he held until his rise to emperor.
Meanwhile, both Caligula's mother and his brother Drusus died in prison.
Caligula was briefly married to Junia Claudilla, in 33, though she died in childbirth the following year.
Caligula spent time befriending the Praetorian prefect, Naevius Sutorius Macro, an important ally.
Quintus Naevius Cordus Sutorius Macro (21 BC – 38 AD) was a prefect of the Praetorian Guard, from 31 until 38, serving under the Roman Emperors Tiberius and Caligula. Upon falling out of favour, he committed suicide. Macro was born in 21 BC at Alba Fucens, a Roman town at the foot of Monte Velino, situated on a hill just to the north of the Via Valeria. Inscriptional evidence from the ruins of this town reveal that, prior to becoming Praetorian prefect, Macro had served as prefect of the vigiles, the Roman fire brigade and night watch. The date of this appointment and the length of his tenure are unknown. Macro was appointed Praetorian prefect by Tiberius after the arrest of Sejanus. According to Tacitus, Macro was active in discrediting Sejanus, and in directing the subsequent purge against his family and followers. As prefect, Macro wielded considerable influence. He furthered his ambitions by befriending Tiberius' grand-nephew Caligula, one of the Emperor's prospective heirs.
Macro spoke well of Caligula to Tiberius, attempting to quell any ill will or suspicion the Emperor felt towards Caligula.
In 35 AD, Caligula was named joint heir to Tiberius's estate along with Tiberius Gemellus.

Death of Tiberius and Early Reign

When Tiberius died on 16 March 37 AD, his estate and the titles of the principate were left to Caligula and Tiberius's own grandson, Gemellus, who were to serve as joint heirs.
Although Tiberius was 78 and on his death bed, some ancient historians still conjecture that he was actually murdered.
Tacitus writes that the Praetorian Prefect, Macro, smothered Tiberius with a pillow to hasten Caligula's accession, much to the joy of the Roman people, while Suetonius writes that Caligula may have carried out the killing, though this is not recorded by any other ancient historian.
Seneca the elder and Philo, who both wrote during Tiberius's reign, as well as Josephus record Tiberius as dying a natural death.
Backed by Macro, Caligula had Tiberius's will nullified with regards to Gemellus on grounds of insanity, but otherwise carried out Tiberius's wishes.
Caligula accepted the powers of the principate as conferred by the senate, and entered Rome on 28 March amid a crowd that hailed him as "our baby" and "our star", among other nicknames.
Caligula is described as the first emperor who was admired by everyone in "all the world, from the rising to the setting sun."
Caligula was loved by many for being the beloved son of the popular Germanicus, and because he was not Tiberius.
Suetonius said that over 160,000 animals were sacrificed during three months of public rejoicing to usher in the new reign.
Philo describes the first seven months of Caligula's reign as completely blissful (!).
Caligula's first acts were said to be generous in spirit, though many were political in nature.
To gain support, he granted bonuses to the military, including the Praetorian Guard, city troops and the army outside Italy.
He destroyed Tiberius's treason papers, declared that treason trials were a thing of the past, and recalled those who had been sent into exile.
He helped those who had been harmed by the imperial tax system, banished certain sexual deviants, and put on lavish spectacles for the public, including gladiatorial games.
Caligula collected and brought back the bones of his mother and of his brothers and deposited their remains in the tomb of Augustus.

Illness and Breakdown

In October 37 AD, Caligula fell seriously ill, or perhaps was poisoned.
He soon recovered from his illness, but many believed that the illness turned the young emperor toward the diabolical: he started to kill off or exile those who were close to him or whom he saw as a serious threat.
Perhaps his illness reminded him of his mortality and of the desire of others to advance into his place.
The evidence from his changed behavior indicates that the 'illness' precipitated a severe nervous breakdown that slowly deteriorated into full-blown paranoid psychosis.
He had his cousin and adopted son Tiberius Gemellus executed – an act that outraged Caligula's and Gemellus's mutual grandmother Antonia Minor.
She is said to have committed suicide, although Suetonius hints that Caligula actually poisoned her. 
He had his father-in-law, Marcus Junius Silanus, and his brother-in-law, Marcus Lepidus, executed as well.
His uncle Claudius was spared only because Caligula preferred to keep him as a laughing stock.
His favorite sister Julia Drusilla,(with whom he may have has an incestuous relationship), died in 38 AD of a fever: his other two sisters, Livilla and Agrippina the Younger, were exiled.
He hated being the grandson of Agrippa, and slandered Augustus by repeating a falsehood that his mother was actually conceived as the result of an incestuous relationship between Augustus and his daughter Julia the Elder.


In AD 38, Caligula focused his attention on political and public reform. He published the accounts of public funds, which had not been made public during the reign of Tiberius. He aided those who lost property in fires, abolished certain taxes, and gave out prizes to the public at gymnastic events. He allowed new members into the equestrian and senatorial orders.
Perhaps most significantly, he restored the practice of democratic elections.
Cassius Dio said that this act "though delighting the rabble, grieved the sensible, who stopped to reflect, that if the offices should fall once more into the hands of the many ... many disasters would result".
During the same year, though, Caligula was criticized for executing people without full trials and for forcing his supporter Macro to commit suicide.

Financial Crisis and Famine

According to Cassius Dio, a financial crisis emerged in AD 39.
Suetonius places the beginning of this crisis in 38.
Caligula's political payments for support, generosity and extravagance had exhausted the state's treasury.
Ancient historians state that Caligula began falsely accusing, fining and even killing individuals for the purpose of seizing their estates.
Historians describe a number of Caligula's other desperate measures.
In order to gain funds, Caligula asked the public to lend the state money.
He levied taxes on lawsuits, weddings and prostitution.
Caligula began auctioning the lives of the gladiators at shows.
Wills that left items to Tiberius were reinterpreted to leave the items instead to Caligula.
Centurions who had acquired property by plunder were forced to turn over spoils to the state.
The current and past highway commissioners were accused of incompetence and embezzlement, and forced to repay money.
In the first year of Caligula's reign he squandered 2.7 billion sesterces that Tiberius had amassed.
His nephew Nero Caesar both envied and admired the fact that Gaius had run through the vast wealth Tiberius had left him in so short a time.
A brief famine of unknown extent occurred, perhaps caused by this financial crisis, but Suetonius claims it resulted from Caligula's seizure of public carriages; according to Seneca, grain imports were disturbed because Caligula re-purposed grain boats for a pontoon bridge.

Construction Projects

Despite financial difficulties, Caligula embarked on a number of construction projects during his reign.
Some were for the public good, though others were for himself.
Josephus describes Caligula's improvements to the harbors at Rhegium and Sicily, allowing increased grain imports from Egypt, as his greatest contributions.
These improvements may have been in response to the famine (see above).
Caligula completed the temple of Augustus and the theater of Pompey, and began an amphitheater beside the Saepta.
He expanded the imperial palace.
He began the aqueducts Aqua Claudia and Anio Novus, which Pliny the Elder considered engineering marvels.
He built a large racetrack known as the 'Circus of Gaius and Nero', and had an Egyptian obelisk (now known as the "Vatican Obelisk") transported by sea and erected in the middle of Rome.
At Syracuse, he repaired the city walls and the temples of the gods.
He had new roads built, and pushed to keep roads in good condition.
He had planned to rebuild the palace of Polycrates at Samos, to finish the temple of Didymaean Apollo at Ephesus, and to found a city high up in the Alps.
He planned to dig a canal through the isthmus in Greece and sent a chief centurion to survey the work.
In 39, Caligula performed a spectacular stunt by ordering a temporary floating bridge to be built using ships as pontoons, stretching for over two miles from the resort of Baiae to the neighboring port of Puteoli.
It was said that the bridge was to rival that of the Persian king, Xerxes, crossing of the Hellespont.
Caligula, who could not swim, then proceeded to ride his favorite horse, Incitatus, across, wearing the breastplate of Alexander the Great.
This act was in defiance of a prediction by Tiberius's soothsayer Thrasyllus of Mendes that Caligula had "no more chance of becoming emperor than of riding a horse across the Bay of Baiae".
Caligula had two large ships constructed for himself, which were recovered from the bottom of Lake Nemi during the dictatorship of Benito Mussolini.
The ships were among the largest vessels in the ancient world.
The smaller ship was designed as a temple dedicated to Diana.
The larger ship was essentially an elaborate floating palace, with marble floors, columns and plumbing.

Problems with the Senate

In AD 39, relations between Caligula and the Roman Senate deteriorated.
The subject of their disagreement is unknown.
A number of factors, though, aggravated this feud.
The Senate had become accustomed to ruling without an emperor between the departure of Tiberius for Capri in AD 26 and Caligula's accession.
Additionally, Tiberius's treason trials had eliminated a number of pro-Julian senators such as Asinius Gallus.
Caligula reviewed Tiberius's records of treason trials and decided, based on their actions during these trials, that numerous senators were not trustworthy.
He ordered a new set of investigations and trials.
He replaced the consul, and had several senators put to death.
Suetonius reports that other senators were degraded by being forced to wait on him and run beside his chariot.
Soon after his break with the Senate, Caligula faced a number of additional conspiracies against him
A conspiracy involving his brother-in-law was foiled in late 39.
Soon afterwards, the Governor of Germany, Gnaeus Cornelius Lentulus Gaetulicus, was executed for connections to a conspiracy.


In AD 40, Caligula expanded the Roman Empire into Mauretania, and made a significant attempt at expanding into Britannia – even challenging Neptune in his campaign.
The conquest of Britannia was fully realized by his successors.
Mauretania was a client kingdom of Rome ruled by Ptolemy of Mauretania. Caligula invited Ptolemy to Rome and then suddenly had him executed.
Mauretania was annexed by Caligula, and subsequently divided into two provinces, Mauretania Tingitana and Mauretania Caesariensis, separated by the river Malua.
Pliny claims that division was the work of Caligula, but Dio states that in 42 AD an uprising took place, which was subdued by Gaius Suetonius Paulinus and Gnaeus Hosidius Geta, and the division only took place after this.
This confusion might mean that Caligula decided to divide the province, but the division was postponed because of the rebellion.
The first known equestrian governor of the two provinces was Marcus Fadius Celer Flavianus, in office in 44 AD.

Caligula's move seemingly had a strictly personal political motive – fear and jealousy of his cousin Ptolemy – and thus the expansion may not have been prompted by pressing military or economic needs, however, the rebellion of Tacfarinas had shown how exposed Africa Proconsularis was to its west, and how the Mauretanian client kings were unable to provide protection to the province, and it is thus possible that Caligula's expansion was a prudent response to potential future threats.

There seems to have been a northern campaign to Britannia that was aborted.
This campaign is derided by ancient historians with accounts of Gauls dressed up as Germanic tribesmen at his triumph and Roman troops ordered to collect seashells as "spoils of the sea".
The few primary sources disagree on what precisely occurred.
Modern historians have put forward numerous theories in an attempt to explain these actions.
This trip to the English Channel could have merely been a training and scouting mission.
Games and the Theater
Caligula held several gladiatorial contests, some in Statilius Taurus's amphitheatre , and others in the Enclosure; diversifying them with prize-fights between the best boxers of Africa and Campania, and occasionally allowing magistrates or friends to preside at these instead of doing so himself. Again, he staged a great number of different theatrical shows in various buildings - sometimes at night, with the whole City illuminated - and would scatter vouchers among the audience entitling them to all sorts of gifts, over and above the basket of food which was everyone's due. At one banquet, noticing with what extraordinary gusto a knight seated opposite dug into the food, he sent him his own heaped plate as well; and rewarded a senator, who had been similarly enjoying himself, with a praetorship, though it was not yet his turn to hold this office. Many all-day Games were celebrated in the Circus and, between races, Caligula introduced panther-baiting and the Trojan war dance. For certain special Games, when all the charioteers were men of senatorial rank, he had the Circus decorated in red and green. Once, while he was inspecting the Circus equipment, from the Gelotian House which overlooks it, a group of people standing in the near-by balconies called out: 'What about a day's racing, Caesar?' So, on the spur of the moment, he gave immediate orders for games to be held.
Caligula the God

He adopted a variety of titles: such as 'Pious', 'Son of the Camp', 'Father of the Army', 'Caesar, Greatest and Best of Men', and when several subject kings came to Rome to pay their respects to him, and argued about their nobility of descent, he cried out "Let there be one lord, one king."
In AD 40, Caligula began implementing very controversial policies that introduced religion into his political role.
Caligula began appearing in public dressed as various gods and demigods such as Hercules, Mercury, Venus and Apollo.
Reportedly, he began referring to himself as a 'god' when meeting with politicians, and he was referred to as "Jupiter" on occasion in public documents.
A sacred precinct was set apart for his worship at Miletus in the province of Asia, and two temples were erected for worship of him in Rome.
The Temple of Castor and Pollux on the forum was linked directly to the imperial residence on the Palatine, and dedicated to Caligula.
He would appear here on occasion, and present himself as a god to the public.
Caligula had the heads removed from various statues of gods and replaced with his own in some temples.
It is said that he wished to be worshiped as "Neos Helios," the "New Sun", indeed, he was represented as a sun god on Egyptian coins.
Caligula's religious policy was a departure from that of his predecessors.
According to Cassius Dio, living emperors could be worshiped as divine in the east, and dead emperors could be worshiped as divine in Rome.
Augustus had the public worship his spirit on occasion, but Dio describes this as an extreme act that emperors generally shied away from.
Caligula took things a step further, and had those in Rome, including senators, worship him as a tangible, living god.
And he nearly assumed a royal diadem then and thereby, doing away with the pretense that he was merely the chief executive of a republic - however, inthe light of what happened to Tarquin, his courtiers dissuaded him from taking such rash action.

Eastern policy

Caligula needed to quell several riots and conspiracies in the eastern territories during his reign.
Aiding him in his actions was his good friend, Herod Agrippa, who became governor of the territories of Batanaea and Trachonitis after Caligula became emperor in AD 37.
The cause of tensions in the east was complicated, involving the spread of Greek culture, Roman Law and the rights of Jews in the empire.
Caligula did not trust the prefect of Egypt, Aulus Avilius Flaccus.
Flaccus had been loyal to Tiberius, had conspired against Caligula's mother, and had connections with Egyptian separatists.
In AD 38, Caligula sent Agrippa to Alexandria unannounced to check on Flaccus.
According to Philo, the visit was met with jeers from the Greek population, who saw Agrippa as the king of the Jews.
Flaccus tried to placate both the Greek population and Caligula by having statues of the emperor placed in Jewish synagogues.
As a result, riots broke out in the city.
Caligula responded by removing Flaccus from his position and executing him.
In AD 39, Agrippa accused Herod Antipas, the tetrarch of Galilee and Perea, of planning a rebellion against Roman rule with the help of Parthia.
Herod Antipas confessed, and Caligula exiled him.
Agrippa was rewarded with his territories.
Riots again erupted in Alexandria in AD 40 between Jews and Greeks.
Jews were accused of not honoring the emperor.
Disputes occurred in the city of Jamnia.
Jews were angered by the erection of a clay altar and destroyed it.
In response, Caligula ordered the erection of a statue of himself in the Jewish Temple of Jerusalem, a demand in conflict with Jewish monotheism.
In this context, Philo wrote that Caligula "regarded the Jews with most especial suspicion, as if they were the only persons who cherished wishes opposed to his".
The Governor of Syria, Publius Petronius, fearing civil war if the order were carried out, delayed implementing it for nearly a year.
Agrippa finally convinced Caligula to reverse the order.


Philo of Alexandria and Seneca the Younger describe Caligula as an insane emperor who was self-absorbed, angry, killed on a whim, and indulged in too much spending and sex.
He is accused of sleeping with other men's wives, and bragging about it, killing for mere amusement, deliberately wasting money on his bridge (see above), causing starvation, and wanting a statue of himself erected in the Temple of Jerusalem for his worship(see above).
Once, at some games at which he was presiding, he ordered his guards to throw an entire section of the crowd into the arena during intermission to be eaten by animals because there were no criminals to be executed, and he was bored.
While repeating the earlier stories, the later sources of Suetonius and Cassius Dio provide additional tales of insanity.
They accuse Caligula of incest with his sisters, Agrippina the Younger, Drusilla, and Livilla, and say he prostituted them to other men.
They state he sent troops on illogical military exercises, turned the palace into a brothel, and, most famously, planned or promised to make his horse, Incitatus, a consul, and actually appointed him a priest.
The validity of these accounts is debatable.
In Roman political culture, insanity and sexual perversity were often presented hand-in-hand with poor government.

Caligula's actions as emperor were described as being especially harsh to the senate, to the nobility and to the equestrian order.
According to Josephus, these actions led to several failed conspiracies against Caligula.
Eventually, officers within the Praetorian Guard led by Cassius Chaerea succeeded in murdering the emperor.
The plot is described as having been planned by three men, but many in the senate, army and equestrian order were said to have been informed of it and involved in it.
The situation had escalated when, in 40 AD, Caligula announced to the senate that he planned to leave Rome permanently and to move to Alexandria in Egypt, where he hoped to be worshiped as a living god.
The prospect of Rome losing its emperor, and thus its political power, was the final straw for many. Such a move would have left both the senate and the Praetorian Guard powerless to stop Caligula's repression and debauchery.
With this in mind Chaerea convinced his fellow conspirators to put their plot into action quickly.
According to Josephus, Chaerea had political motivations for the assassination.
Suetonius sees the motive in Caligula calling Chaerea derogatory names.
Caligula considered Chaerea effeminate because of a weak voice, and for not being firm with tax collection.
Caligula would mock Chaerea with names like "Priapus" and "Venus".
On 22 January 41 Cassius Chaerea and other guardsmen accosted Caligula as he addressed an acting troupe of young men during a series of games and dramatics held for the Divine Augustus.
Details recorded on the events vary somewhat from source to source, but they agree that Chaerea stabbed Caligula first, followed by a number of conspirators.
Suetonius records that Caligula's death resembled that of Julius Caesar.
He states that both the elder Gaius Julius Caesar (Julius Caesar) and the younger Gaius Julius Caesar (Caligula) were stabbed 30 times by conspirators led by a man named Cassius (Cassius Longinus and Cassius Chaerea).
By the time Caligula's loyal Germanic guard responded, the Emperor was already dead.
The Germanic guard, stricken with grief and rage, responded with a rampaging attack on the assassins, conspirators, innocent senators and bystanders alike.
The senate attempted to use Caligula's death as an opportunity to restore the republic.
Chaerea tried to persuade the military to support the senate.
The military, though, remained loyal to the idea of the Principate
The grieving Roman people assembled and demanded that Caligula's murderers be brought to justice.
Uncomfortable with lingering imperial support, the assassins sought out and stabbed Caligula's wife, Caesonia, and killed their young daughter, Julia Drusilla, by smashing her head against a wall.
They were unable to reach Caligula's uncle, Claudius; after a soldier, Gratus, found Claudius hiding behind a palace curtain he was spirited out of the city by a sympathetic faction of the Praetorian Guard to the nearby Praetorian camp.
Claudius became emperor after procuring the support of the Praetorian Guard.
He ordered the execution of Chaerea, and of any other known conspirators involved in the death of Caligula.
According to Suetonius, Caligula's body was placed under turf until it was burned and entombed by his sisters.
He was buried within the Mausoleum of Augustus.


All surviving sources, except Pliny the Elder, characterize Caligula as insane, however, it is not known whether they are speaking figuratively or literally.
Additionally, given Caligula's unpopularity among the surviving sources, it is difficult to separate fact from fiction.
Recent sources are divided in attempting to ascribe a medical reason for his behavior, citing as possibilities encephalitis, epilepsy or meningitis.
Philo of Alexandria, Josephus and Seneca state that Caligula was insane, but describe this madness as a personality trait that came through experience.
Seneca states that Caligula became arrogant, angry and insulting once becoming emperor, and used his personality flaws as examples his readers can learn from.
According to Josephus, power made Caligula incredibly conceited, and led him to think he was a god.
Philo of Alexandria reports that Caligula became ruthless after nearly dying of an illness in the eighth month of his reign in AD 37.
Juvenal reports he was given a magic potion that drove him insane.
Suetonius said that Caligula suffered from "falling sickness", or epilepsy, when he was young (similar to Gaius Julius Caesar).
Modern historians have theorized that Caligula lived with a daily fear of seizures.
Despite swimming being a part of imperial education, Caligula could not swim.
Epileptics are discouraged from swimming in open waters because unexpected fits in such difficult rescue circumstances can be fatal.
Additionally, Caligula reportedly talked to the full moon, and epilepsy was long associated with the moon.
Some modern historians also suggest that Caligula suffered from hyperthyroidism.
This diagnosis is mainly attributed to Caligula's irritability and his "stare" as described by Pliny the Elder.

© Copyright Peter Crawford 2016