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Gaius (Caligula) (A.D. 37-41)

Garrett G. Fagan

Pennsylvania State University

A Bust of theEmperor Caligula


Gaius Caesar Augustus Germanicus (b. A.D. 12, d. A.D. 41, emperor A.D. 37-41) represents a turning point in the early history of the Principate. Unfortunately, his is the most poorly documented reign of the Julio-Claudian dynasty. The literary sources for these four years are meager, frequently anecdotal, and universally hostile.[[1]] As a result, not only are many of the events of the reign unclear, but Gaius himself appears more as a caricature than a real person, a crazed megalomaniac given to capricious cruelty and harebrained schemes. Although some headway can be made in disentangling truth from embellishment, the true character of the youthful emperor will forever elude us.

Gaius's Early Life and Reign

Gaius was born on 31 August, A.D. 12, probably at the Julio-Claudian resort of Antium (modern Anzio), the third of six children born to Augustus's adopted grandson, Germanicus, and Augustus's granddaughter, Agrippina. As a baby he accompanied his parents on military campaigns in the north and was shown to the troops wearing a miniature soldier's outfit, including the hob-nailed sandal called caliga, whence the nickname by which posterity remembers him.[[2]] His childhood was not a happy one, spent amid an atmosphere of paranoia, suspicion, and murder. Instability within the Julio-Claudian house, generated by uncertainty over the succession, led to a series of personal tragedies. When his father died under suspicious circumstances on 10 October A.D. 19, relations between his mother and his grand-uncle, the emperor Tiberius, deteriorated irretrievably, and the adolescent Gaius was sent to live first with his great-grandmother Livia in A.D. 27 and then, following Livia's death two years later, with his grandmother Antonia. Shortly before the fall of Tiberius's Praetorian Prefect, Sejanus, in A.D. 31 he was summoned to join Tiberius at his villa on Capri, where he remained until his accession in A.D. 37. In the interim, his two brothers and his mother suffered demotion and, eventually, violent death. Throughout these years, the only position of administrative responsibility Gaius held was an honorary quaestorship in A.D. 33. [[3]]

When Tiberius died on 16 March A.D. 37, Gaius was in a perfect position to assume power, despite the obstacle of Tiberius's will, which named him and his cousin Tiberius Gemellus joint heirs. (Gemellus's life was shortened considerably by this bequest, since Gaius ordered him killed within a matter of months.) Backed by the Praetorian Prefect Q. Sutorius Macro, Gaius asserted his dominance. He had Tiberius's will declared null and void on grounds of insanity, accepted the powers of the Principate as conferred by the Senate, and entered Rome on 28 March amid scenes of wild rejoicing. His first acts were generous in spirit: he paid Tiberius's bequests and gave a cash bonus to the Praetorian Guard, the first recorded donativum to troops in imperial history. He honored his father and other dead relatives and publicly destroyed Tiberius's personal papers, which no doubt implicated many of the Roman elite in the destruction of Gaius's immediate family. Finally, he recalled exiles and reimbursed those wronged by the imperial tax system [[4]]. His popularity was immense. Yet within four years he lay in a bloody heap in a palace corridor, murdered by officers of the very guard entrusted to protect him. What went wrong?

Gaius's "Madness"

The ancient sources are practically unanimous as to the cause of Gaius's downfall: he was insane. The writers differ as to how this condition came about, but all agree that after his good start Gaius began to behave in an openly autocratic manner, even a crazed one. [[5]] Outlandish stories cluster about the raving emperor, illustrating his excessive cruelty, immoral sexual escapades, or disrespect toward tradition and the Senate. The sources describe his incestuous relations with his sisters, laughable military campaigns in the north, the building of a pontoon bridge across the Bay at Baiae, and the plan to make his horse a consul. [[6]] Modern scholars have pored over these incidents and come up with a variety of explanations: Gaius suffered from an illness; he was misunderstood; he was corrupted by power; or, accepting the ancient evidence, they conclude that he was mad.[[7]] However, appreciating the nature of the ancient sources is crucial when approaching this issue. Their unanimous hostility renders their testimony suspect, especially since Gaius's reported behavior fits remarkably well with that of the ancient tyrant, a literary type enshrined in Greco-Roman tradition centuries before his reign. Further, the only eye-witness account of Gaius's behavior, Philo's Embassy to Gaius, offers little evidence of outright insanity, despite the antagonism of the author, whom Gaius treated with the utmost disrespect. Rather, he comes across as aloof, arrogant, egotistical, and cuttingly witty -- but not insane. The best explanation both for Gaius's behavior and the subsequent hostility of the sources is that he was an inexperienced young man thrust into a position of unlimited power, the true nature of which had been carefully disguised by its founder, Augustus. Gaius, however, saw through the disguise and began to act accordingly. This, coupled with his troubled upbringing and almost complete lack of tact led to behavior that struck his contemporaries as extreme, even insane.

Gaius and the Empire

Gaius's reign is too short, and the surviving ancient accounts too sensationalized, for any serious policies of his to be discerned. During his reign, Mauretania was annexed and reorganized into two provinces, Herod Agrippa was appointed to a kingdom in Palestine, and severe riots took place in Alexandria between Jews and Greeks. These events are largely overlooked in the sources, since they offer slim pickings for sensational stories of madness. [[8]] Two other episodes, however, garner greater attention: Gaius's military activities on the northern frontier, and his vehement demand for divine honors. His military activities are portrayed as ludicrous, with Gauls dressed up as Germans at his triumph and Roman troops ordered to collect sea-shells as "spoils of the sea." Modern scholars have attempted to make sense of these events in various ways. The most reasonable suggestion is that Gaius went north to earn military glory and discovered there a nascent conspiracy under the commander of the Upper German legions, Cn. Lentulus Gaetulicus. The subsequent events are shrouded in uncertainty, but it is known that Gaetulicus and Gaius's brother-in-law, M. Aemilius Lepidus, were executed and Gaius's two surviving sisters, implicated in the plot, suffered exile. [[9]] Gaius's enthusiasm for divine honors for himself and his favorite sister, Drusilla (who died suddenly in A.D. 38 and was deified), is presented in the sources as another clear sign of his madness, but it may be no more than the young autocrat tactlessly pushing the limits of the imperial cult, already established under Augustus. Gaius's excess in this regard is best illustrated by his order that a statue of him be erected in the Temple at Jerusalem. Only the delaying tactics of the Syrian governor, P. Petronius, and the intervention of Herod Agrippa prevented riots and a potential uprising in Palestine. [[10]]

Conspiracy and Assassination

The conspiracy that ended Gaius's life was hatched among the officers of the Praetorian Guard, apparently for purely personal reasons. It appears also to have had the support of some senators and an imperial freedman. [[11]] As with conspiracies in general, there are suspicions that the plot was more broad-based than the sources intimate, and it may even have enjoyed the support of the next emperor Claudius, but these propositions are not provable on available evidence. On 24 January A.D. 41 the praetorian tribune Cassius Chaerea and other guardsmen caught Gaius alone in a secluded palace corridor and cut him down. He was 28 years old and had ruled three years and ten months. [[12]]


Whatever damage Tiberius's later years had done to the carefully crafted political edifice created by Augustus, Gaius multiplied it a hundredfold. When he came to power in A.D. 37 Gaius had no administrative experience beyond his honorary quaestorship, and had spent an unhappy early life far from the public eye. He appears, once in power, to have realized the boundless scope of his authority and acted accordingly. For the elite, this situation proved intolerable and ensured the blackening of Caligula's name in the historical record they would dictate. The sensational and hostile nature of that record, however, should in no way trivialize Gaius's importance. His reign highlighted an inherent weakness in the Augustan Principate, now openly revealed for what it was -- a raw monarchy in which only the self-discipline of the incumbent acted as a restraint on his behavior. That the only means of retiring the wayward princeps was murder marked another important revelation: Roman emperors could not relinquish their powers without simultaneously relinquishing their lives.


The bibliography on Gaius is far too vast for comprehensive citation here. Most of the ancient material can be found in Gelzer and Smallwood. Ample reference to relevant secondary works is made in Barrett, Caligula (319-28) and Hurley (219-30). The works listed below are therefore either the main treatments of Gaius or are directly pertinent to the issues discussed in the entry above.

Balsdon, J.P.V.D. The Emperor Gaius. Oxford, 1934.

________. "The Principates of Tiberius and Gaius." ANRW 2.2 (1975): 86-94.

Barrett, A.A. Caligula: The Corruption of Power. New Haven, 1989.

________. Agrippina. Sex, Power, and Politics in the Early Empire. New Haven, 1996.

Benediktson, D.T. "Caligula's Madness: Madness or Interictal Temporal Lobe Epilepsy?" Classical World 82 (1988-89), 370-5.

Bicknell, P. "The Emperor Gaius' Military Activities in AD 40." Historia 17 (1968): 496-505.

Bilde, P. "The Roman Emperor Gaius (Caligula)'s Attempt to Erect his Statue in the Temple of Jerusalem." STh 32 (1978): 67-93.

Boschung, D. Die Bildnisse des Caligula. Berlin, 1989.

Charlesworth, M.P. "The Tradition About Caligula" Cambridge Historical Journal 4 (1933): 105-119.

Davies, R.W. "The Abortive Invasion of Britain by Gaius." Historia 15 (1966): 124-28.

D'Ecré, F. "La mort de Germanicus et les poisons de Caligula." Janus 56 (1969): 123-48.

Ferrill, A. Caligula, Emperor of Rome. London, 1991.

Gelzer, M. "Iulius Caligula." Real-Enzyclopädie 10.381-423 (1919).

Grant, M. The Roman Emperors. A Biographical Guide to the Rulers of Imperial Rome 31 BC - AD 476 (New York, 1985), 25-28.

Hurley, D.W. "Gaius Caligula in the Germanicus Tradition." American Journal of Philology 110 (1989): 316-38.

________. An Historical and Historiographical Commentary on Suetonius' Life of C. Caligula. Atlanta, 1993.

Jerome, T.S. "The Historical Tradition About Gaius," in id., Aspects of the Study of Roman History. New York, 1923.

Katz, R.S. "The Illness of Caligula." Classical World 65 (1971-72): 223-5

McGinn, T.A.J. "Caligula's Brothel on the Palatine," EMC 42 (1998): 95-107.

Massaro, V. and I. Montgomery. "Gaius: Mad Bad, Ill or All Three?" Latomus 37 (1978): 894-909

________. "Gaius (Caligula) Doth Murder Sleep." Latomus 38 (1979): 699-700.

Maurer, J. A. A Commentary on C. Suetoni Tranquilli, Vita C. Caligulae Caesaris, Chapters I-XXI. Philadelphia, 1949.

Morgan, M.G. "Caligula's Illness Again." Classical World 66 (1972-73): 327-9

Philips, E.J. "The Emperor Gaius' Abortive Invasion of Britain." Historia 19 (1970): 369-74.

Simpson, C. J. "The 'Conspiracy' of AD 39." In Studies in Latin Literature and Roman History II, edited by C. Deroux, 347-66. Brussels, 1980.

Smallwood, E.M. (ed.). Documents Illustrating the Principates of Gaius, Claudius and Nero. Cambridge. 1967.

Wardle, D. Suetonius' Life of Caligula: A Commentary. Brussels, 1994.

Woods, D. "Caligula's Seashells." Greece and Rome 47 (2000): 80-87.

Wood, S. "Diva Drusilla Panthea and the Sisters of Caligula." AJA 99 (1995): 457-82.


[[1]] The main ancient sources for Gaius's reign are: Suet. Gaius; Dio 59; Philo In Flaccum and Legatio ad Gaium; Jos. AJ 19.1-211. Tacitus's account of the reign is lost. However, he makes occasional references to Gaius in the extant portions of his works, as does Seneca. All of these sources have reason to be hostile to Gaius's memory: Seneca's style was roundly abused by the emperor (Suet. Gaius 53.2; Dio 59.19.7-8); Philo and Josephus, as Jews, resented Gaius's blasphemous demands for divinity that almost roused Palestine to rebellion (see above, Gaius and the Empire); and the later sources inherited a tradition about Gaius that can be shown to be biased and exaggerated, cf. Charlesworth, "The Tradition about Gaius." Besides these literary sources, inscriptions and coins also offer some information, see Smallwood, Documents Illustrating.

[[2]] Tac. Ann. 1.41.3; Suet. Gaius 9.1.

[[3]] Death of Germanicus and aftermath: Tac. Ann. 2.69-3.19; Gaius with Livia, Antonia, and Tiberius: Tac. Ann. 6.20.1; Suet. Gaius 10.1, 23.2; fate of Agrippina: Tac. Ann. 5.3.2 - 5.5.2, 6.25.1; and of Nero and Drusus Caesar: Tac. Ann. 5.3.2, 6.23.4-5, Suet. Tib. 54, Gaius 7; Gaius's quaestorship: Dio 58.23.1. For the alleged involvement of Gaius in his father's death, see D'Ecré, "La mort de Germanicus."

[[4]] Early reign and first acts: Suet. Gaius 13-16; Philo Leg. 8-13; Dio 59.2-3. Macro's full name: Smallwood, Documents Illustrating, no. 254. Date of Gaius's arrival in Rome: Acta Fratrum Arvalium (Smallwood, Documents Illustrating, no. 3.15-17). Gemellus: Suet. Gaius 14.1, 15.2, 23.3; Dio 59.1.2-3, 59.8.1-2; Philo Leg. 23-31.

[[5]] Seneca, without explanation, believes he went mad (Brev. 18.5-6; Helv. 10.4; Tranqu. 14.5; Ben. 7.11.2). Josephus also thinks that Gaius went mad but alludes to a love-potion administered by his wife Caesonia as the cause (AJ 19.193), apparently after two years of good rule (AJ 18.256). Philo blames an illness in the fall of A.D. 37 (Leg. 14-22). Suetonius mentions simply a "brain sickness" (valitudo mentis; Gaius 51.1). Dio thinks that faults of character led to a deterioration in his behavior (59.3-4). Surviving references suggest that Tacitus thought Gaius at least of troubled and impulsive mind, which is not the same thing as crazed (Agr. 13.2; Ann. 6.20.1, 6.45.5, 13.3.6; Hist. 4.48.2).

[[6]] Incest: Suet. Gaius 24.1; Dio 59.3.6; Jos. AJ 19.204. Military campaigns: Tac. Hist. 4.15.3, Germania 37.5, Suet. Gaius 43-46, Dio 59.21.1-3. Bridge at Baiae: Suet. Gaius 19; Dio 59.17; Jos. AJ 19.5-6. Horse as consul: Suet. Gaius 55.3; Dio 59.14.7; His alleged setting up of a brothel in the palace may contain a kernel of truth, even if the story is much embellished, see T.A.J. McGinn, "Caligula's Brothel on the Palatine," EMC 42 (1998): 95-107.

[[7]] Alcoholism: Jerome, "Historical Tradition"; hyperthyroidism/thyrotoxicos: Katz, "Illness of Caligula"; mania: Massaro and Montgomery, "Gaius: Mad, Bad, Ill or All Three" and "Gaius (Caligula) Doth Murder Sleep"; epilepsy: Benediktson, "Caligula's Madness." Morgan ("Caligula's Illness Again") makes some astute observations on the weakness of the medical approach as a whole. He points out that the ancient concept of physiognomy -- that people's characters are manifest in their appearance -- makes any diagnosis highly suspect. In fact, all such medical explanations are doomed to failure. The sources simply cannot be trusted, and diagnosing a patient 2,000 years dead is, at best, a stretch. Balsdon (The Emperor Gaius) argued that Gaius was misunderstood and attempted to offer rational explanations for all of his apparently deranged antics. A useful summary and critique of "madness" theories is to be found in Barrett, Caligula, 213-41. For a recent acceptance of the madness thesis, cf. Ferrill, Caligula, Emperor of Rome.

[[8]] Mauretania: Dio 59.25.1; see also Barrett, Caligula, 115-20. Agrippa: Jos. AJ 18.228-37; Phil Leg. 324-26; see also E. M. Smallwood, The Jews under Roman Rule (Leiden, 1976), 187-200. Alexandrian riots: Philo Flacc and Leg.

[[9]] Fake Germans in triumph: Suet. Gaius 47. Military campaigns: see above, note [6]. For modern rationalizations of these campaigns, cf., e.g., Bicknell, "Military Activities"; Davies, "Abortive Invasion"; Philips, "Abortive Invasion"; Barrett, Caligula, 125-39, and Woods, "Caligula's Seashells.". Execution of Gaetulicus and exile of sisters: the Gaetulicus affair is ably assessed in Barrett, Caligula, 91-113, and id. Agrippina, 60-70; for a contrasting view, see Simpson, "The 'Conspiracy' of AD 39."

[[10]] The Jerusalem affair is described most fully by Josephus (AJ 18.261-309; BJ 2.184-203) and Philo (Leg. 188, 198-348). Thorough modern assessments can be found in Barrett, Caligula, 188-91, cf. 140-53 (on Gaius's demand for divine honours, which Barrett argues are exaggerated by the sources); Bilde "Statue in the Temple"; and Smallwood, Jews (above, note [8]), 174-80. Drusilla: Suet. Gaius 24.2-3; Dio 59.11; Smallwood, Documents Illustrating, nos 5.12-15, 11, 128, 401.12; Wood, "Diva Drusilla."

[[11]] The named Praetorian conspirators include three tribunes -- Cassius Chaerea (Suet. Gaius 56.2; Dio 59.29.1; Sen. Const. 18.3; Jos. AJ 19.18, 21, 28-37); Cornelius Sabinus (Suet. Gaius 58.2; Dio 59.29.1; Jos. AJ 19.46, 48, 261); Papinius (Jos. AJ 19.37) -- and the Prefect M. Arrecinus Clemens (Jos. AJ 19.37-46). Senators associated with the plot are M. Annius Vinicianus (Jos. AJ 19.18, 20, 49-51), M. Valerius Asiaticus (Tac. Ann. 11.1.2), Cluvius Rufus and L. Nonius Asprenas (Jos. AJ 19.91-92, 98). Gaius's freedman Callistus is also a named participant (Tac. Ann. 11.29.1; Dio 29.29.1; Jos. AJ 19.63-69).

[[12]] The possible involvement of Claudius in the plot is assessed by B. Levick, Claudius (New Haven, 1990), 33-39. The fullest account of the assassination is that of Josephus (AJ 19.70-113), with more summary accounts found in Suetonius (Gaius 58) and the epitome of Dio (59.29.5-7).

Copyright © 1997, Garrett G. Fagan. This file may be copied on the condition that the entire contents, including the header and this copyright notice, remain intact.

Comments to: Garrett G. Fagan

Updated: 28 October 2004

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