Under Caligula the senators had been confronted with unprecedented experiences. They could not accuse him of committing murder arbitrarily; instead he had simply let them give free rein to their servility and cynically taken it at face value. He had held up a mirror to the Roman aristocracy and showed them the absurdity of their own behavior. In so doing he had made them look ridiculous and let them humiliate themselves as never before. Utterly powerless, they had been forced to tolerate his game and join in it. What form did their “still rankling hatred” take after his death?
A good clue is available in the speech given in the Senate by consul Sentius Saturninus after the assassination, which Josephus quotes from his Roman source. The consul fell back on a long-standing pattern and accused Caligula of extreme tyranny. Clearly it never crossed anyone’s mind to call him insane. Why should it have? The men leading the debate in the Senate had remained the emperor’s aristocratic followers until the end, and if they had advanced the implausible claim that they had been serving a madman, they would have only created new embarrassments for themselves and the aristocracy as a whole.
Seneca is the first to speak of Caligula’s madness (furor and insania) in his writings, which date from not long afterwards. If one examines these passages more closely, however, it emerges that he is not passing judgment on the deceased emperor’s mental health, but is rather filled with hatred and accusing him of tyrannical behavior and the annihilation of freedom. He deplores the ignominy that this has brought on the Roman Empire. Seneca uses “insanity” as a term of abuse, to censure immorality and the violation of all aristocratic conventions. He uses the term in a similar sense when he speaks of women so extravagant that they wore earrings worth more than the combined fortunes of two or three aristocratic families. Finally, it is noteworthy that in various places in his writings he excoriates Alexander the Great in almost exactly the same language, as an “insane” and “megalomaniacal” young man — a parallel to which Caligula would have had no objection.
In the writings of the Jewish authors Philo and Josephus, the allegation of mania is directly connected to Caligula’s demand that he be venerated as divine. Here, too, the word is used in a derogatory sense to reflect what Jews regarded as blasphemy on the emperor’s part and the threats to the Jewish people that had arisen from this. As we have seen, the emperor himself shows no signs of psychopathology in the descriptions of either author; on the contrary, Philo recognizes his particular psychological skill in seeing through the motives of his interlocutors, while Josephus credits him with superior rhetorical abilities.
Pliny the Elder, who refers to Caligula’s insania, uses the word in the context of the emperor’s construction projects in Rome and goes on to note in the same sentence that his “insanity” was surpassed by Marcus Scaurus, Sulla’s stepson, whose houses were even more luxurious and extravagant. Tacitus refers to the “troubled brain” (turbata mens) of the emperor but goes on to say that “it did not affect his power of speech” (Tac. Ann. 13.3.2). Tacitus is also intent on pronouncing a moral verdict against the emperor, as appears in the other passages where he mentions Caligula. He repeatedly uses such terms as “capriciousness,” “malice,” “dissimulation,” “cunning,” and “irascibility.” It is thus not surprising that Caligula is by no means the only emperor who was called “insane.” The same description was applied to Tiberius, Claudius, and Nero.
Who came up with the idea that Caligula was truly mentally ill? Among the extant works by ancient authors it is Suetonius who raises the claim first. The emperor, he writes, was in poor health both physically and mentally. He suffered from epilepsy as a child and later from sudden attacks of fainting as well. Sudden fits of anxiety, severe insomnia, and confused images in dreams plagued him. Suetonius reports further that Caligula was aware of his own mental illness and reflected on possibilities for “clearing his brain” (de purgando cerebro). Thus it was almost a century before the term of abuse was reified and the Roman aristocracy that had suffered under Caligula received this dubious restitution of its honor. And the diagnostician was not a senator but a former imperial secretary from the equestrian order, who pursued antiquarian studies and studded his biographies of the emperors with anecdotes. He explains Caligula’s condition by adding the comment: “It is thought that his wife Caesonia gave him a drug intended for a love potion, which however had the effect of driving him mad” (Suet. Cal. 50.2).
It remains an open question how much Suetonius added to the invention of the mad emperor and how much he borrowed from earlier documents (containing expressions of fresh hatred that historians like Tacitus did not consider worth passing on). What we do know is that his biography of Caligula decisively influenced the way the emperor was perceived from then on. Suetonius composed it at a time when, after more than a century of bloody conflicts between emperors and aristocracy, peace and a spirit of accommodation defined their relations. Rulers from Nerva to Marcus Aurelius (A.D. 96–180) displayed aristocratic modesty, and the senatorial aristocracy seems to have learned to live with imperial rule, which had taken on a form they could endure. In these circumstances the memory of an emperor who had tried to establish an undisguised monarchy, who had humiliated aristocrats and given them a taste of what imperial power really meant, must have been very annoying. It was much more pleasant to declare that if an emperor strove to create a monarchy he was a mentally diseased tyrant, who rightly and necessarily came to a dreadful end. Suetonius’s contemporaries in the second century saw precisely this intention in his biography of Caligula; this is demonstrated by the fate of a Roman in the time of the emperor Commodus, which bears a certain resemblance to the experience of Ludwig Quidde nearly two thousand years later. When the son of Marcus Aurelius came to the throne at the age of nineteen and was confronted right at the start of his reign with a conspiracy among the leaders of the senatorial aristocracy, the existing accommodation came to an abrupt end. Force and undisguised autarchy once again shaped the age. Commodus, it is reported, had someone thrown to wild beasts to be devoured because the man had read Suetonius’s Life of Gaius Caligula.
Commodus was murdered, too, and the message of Suetonius’s biography of Caligula lent his portrait plausibility in the following centuries. In an abbreviated late-fourth-century history of the emperors the section on Caligula describes his cruelty, incest, and declaration of his own divinity, and then continues: “Perhaps it would have been more fitting not to preserve this for posterity. It is useful to know all the actions of the emperors, however, so that the bad ones among them may avoid similar deeds, if only out of fear for their reputation in future generations” (Epitome de Caesaribus 3.6). The writer of this passage was unaware that the kind of monarchy envisioned by Caligula had more than a little similarity to the imperial rule of his own day: From the reigns of Diocletian (284–305) and Constantine (324–37), emperors appeared in jewel-studded robes and were venerated in a complicated ceremony requiring aristocrats to prostrate themselves and kiss the hem of the imperial purple robe. And the emperors had also deserted Rome, leaving behind the senatorial society there and establishing a new center of rule in Constantinople.