Roman Imperial Cult: Evidence from the Arval Brotherhood

The Arval Brothers were a Roman state college of 12 priests traditionally responsible for the cult of Dea Dia, a goddess of fertility and growth sometimes identified with Ceres, at her sacred grove on the Via Campania.

By the late republic, the priesthood had dwindled in importance, but was rejuvenated by Augustus (27 BCE-14 CE), under whom they also began to conduct imperial cult rituals, sacrificing to various deities in gratitude for the safety and prosperity of the emperor, or benefactions bestowed on the state through his actions. The emperor was often a member of the brotherhood, highlighting its importance.

From this time until at least the end of the 3rd century CE, the Arvals set up annual records on stelae in their grove describing their rituals in varying detail, listing their date, location, purpose, which victims were sacrificed to which deities, who conducted the rituals, and which brothers were present. The Acta Fratrum Arvalium have no surviving parallels, and their purpose is unknown. However, based on prosopographical evidence and the nature and location of their rituals, it seems likely that Augustus made the Arvals one of the most important colleges in Rome, and that their practices probably reflect wider trends in the state cult.

While the surviving records of the Arvals are fragmentary, they provide a broad overview of the imperial cult. So, what kinds of imperial cult rituals did the Arvals practice? For the sake of clarity and brevity, this article will focus exclusively on the reigns of Rome’s first imperial dynasty, the Julio-Claudians.

State Powers and Benefactions

Under the Julio-Claudians, the events most often marked with sacrifices by the Arval Brothers were the days on which the emperor received state powers, and the anniversaries of those days throughout the rest of his reign.  These days represented the earthly sources of the power of the emperor, and these rituals may have sanctified them annually.

This pattern of anniversary cult is made clear from the surviving Arval evidence from the reigns of Gaius Caligula (37-41 CE) and Nero (54-68 CE), for which a few complete years survive. 

Under Caligula, the Arvals conducted cult on the anniversaries of the days on which he was first hailed imperator (March 18^th 37 CE), which represented power over Rome’s armed forces, when he first entered the city as princeps (March 28^th 37 CE), and when he assumed the title pater patriae, meaning “father of his country,” making him the paterfamilias or head of household of the Roman state(September 21^st 38 CE).  Although not an anniversary per se, Caligula’s assumption of his second consulship on January 1^st 39 CE, was also sanctified by the Arvals with sacrifices. Consulship rituals appear to fall into the same category as anniversary cult as they also related to earthly powers bestowed on the emperor by the state, and sanctified them for the year.  

A similar calendar of anniversary cultprobably continued to be conducted under Claudius (41-54 CE), for although the Acta Fratrum Arvalium from his reign are very fragmentary, a definite example survives of a rite conducted on the anniversary of his assumption of the title pater patriae (January 12^th 42 CE) in an unknown year, suggesting that the same general pattern continued. 

Under Nero anniversary cult was conducted annually for his assumption of tribunicia potestas, which made him sacrosanct and allowed him to veto the proposals of any magistrate(December 4^th 54 CE)and imperium (October 13^th 54 CE), and rites were also undertaken for his assumption of the consulship in various years.

These types of anniversaries appear to have been important in the imperial cult from the very beginning of Imperial Rome.  Although little remains from the Acta Fratrum Arvalium from the reigns of Augustus and Tiberius (14-37 CE), many contemporary calendars survive from throughout Italy in which similar daysare marked as holidays.  Although these calendars were produced by a variety of different groups, such as municipal governments or collegial affiliations, they were most likely derived from an official Roman example.  This is indicated by the fact that, accounting for additions over time, the calendars are consistent with one another, and their content is verified by literary sources, including Augustus’ Res Gestae and Ovid’s Fasti.

For Augustus, days on which he bestowed important benefactions on Rome – such as his victory at Alexandria which saved Rome from Marcus Antonius and Cleopatra and his restoration of the res publica – and days that saw him take up earthly powers – such as the day he first took up the fasces, the day he first assumed the consulship, the day the senate awarded him the title Augustus and the day he became Pontifex Maximus (chief priest)– were recorded as festive days in the calendars.  Tiberius’ military victory at Illyricum was similarly noted, as was his assumption of earthly powers, such as the role of Pontifex Maximus following Augustus’ death. 

The Augustan and Tiberian cult calendars differ from the Arval calendar under the later Julio-Claudians in that benefactions, seemingly marked annually under Augustus and Tiberius, were marked by the Arvals under the Julio-Claudians with singular, extraordinary rituals rather than annual cult. Furthermore, in addition to the benefactions bestowed on Rome by the emperorbeing marked with extraordinary cult, under the Julio-Claudians, benefactions received by the emperor, such as the detection of conspiracies against him, also appear to have been marked by the Arvals with extraordinary cult. The Arval records from Nero’s reign preserve testimony of extraordinary cult conducted for Nero’s departure to war and military victories, the detection of conspiracies, the safe pregnancy of Nero’s wife Poppaea, and for Nero’s various adventus (arrivals in Rome).  Each occasion saw a one-off Arval ritual that was not repeated in later years. 

These slight differences in cult patterns may indicate that while under Augustus the emperor’s actions on behalf of Rome were considered a primary source of and justification for his power and position in the state, by the reigns of Caligula, Claudius and Nero, imperial power had become institutionalised, and it was the powers granted to them by the state that were considered the primary source of their position. 

Birthday Cult

Alongside his official powers, the dynastic source of Tiberius’ power was also recognised in the calendars, as his adoption by Augustus (June 26^th 4 CE) was a holiday. This source of imperial power also appears to have been important in the Arval cult conducted under the later Julio-Claudians, as Nero’s adoption by Claudius also saw annual sacrifices from the Arvals throughout Nero’s reign (February 25^th 50 CE).

ob natalem Neroni… immolauit Iovi optimo maximo bouem marem Iunoni vaccam Minerva vaccam Saulti publicae vaccam Genio ipsius taurum…

On account of the birthday of Nero… an ox was sacrificed to Jupiter Optimus Maximus, a cow to Juno, a cow to Minerva, a cow to Salus Publica and a bull to his Genius…

The importance of the role of the Julio-Claudian family and bloodline in justifying and securing the power of the emperorwas also incorporated into cult calendars through the frequent celebration of imperial birthdays.  According to the surviving calendars and other sources, at various different times under Augustus and Tiberius, the birthdays of both emperorsand also Augustus’ wife and Tiberius’ mother Livia, Augustus’ grandsons Gaius Caesar, Lucius Caesar, Tiberius’ brother Drusus and his son Germanicus, and probably also Germanicus’ sons Nero and Drusus, were all festive days. 

Similarly, many imperial birthdays were marked with annual rituals by the Arvals.  Under Caligula, sacrifices were undertaken on the birthdays of the emperor, the deceased Tiberius and Livia, Caligula’s grandmother Antonia Minor, his deceased father Germanicus, and mother Agrippina, and on the birthdays of Divus Augustus, the posthumously deified Augustus, and Diva Drusilla, Caligula’s sister whom he had deified, though not on Drusilla’s birthday during her lifetime.

The only references to birthday rites from the extremely fragmentary Arval records from Claudius’ reign are to Divus Augustus’ birthday in unknown years, but similar cult may have continued as according to Cassius Dio equestrian games were held on Claudius’ birthday, the Praetorians observed the birthdays of Claudius’ wife Messalina and son Britannicus, and Claudius introduced public games on the birthdays of his deceased father Drusus and mother Antonia.

Under Nero, cult was undertaken on the birthdays of the emperor, his mother Agrippina, and his wives during their lives, and on the birthday of Nero’s deceased biological father, Domitius Ahenobarbus.

According to the Arval records, under Tiberius and early in Caligula’s reign, birthdays simply saw sacrifices to Jupiter, but later in Caligula’s reign, Jupiter was joined by the rest of the Capitoline Triad. By the reign of Nero, they were also joined by the divi, the collection of deified members of the imperial family, and the Genius (tutelary deity) of the emperor.

This plethora of imperial birthdays marked with cult would have given the Julio-Claudian dynasty an unmistakable presence in the Roman state cult, and the inclusion of dynastic deities such as the divi and Geniusin the pantheon by the reign of Nero indicates the role of these rituals in highlighting the dynastic source of imperial power.

Annual Vota

Another imperial cult ritual consistently conducted by the Arvals was the January 3^rd vota. The conception of the January 3^rd votaprobably dates from the time of Julius Caesar, when the Senate decreed that vows and sacrifices should be conducted annually for Caesar’s welfare (Cassius Dio 44.6.1). This probably involved including Caesar’s welfare alongside that of the state in the votafor its prosperity conducted annually on January 1^st.

During this January 1^st ritual, led by the consuls, victims were promised to the Capitoline Triad and Salus(health) on the same day the following year if they preserved the safety of the state, and the victims promised the previous year were sacrificed. Augustus confirms that the senate ordered the consuls and priests to conduct vows for his well-being every five years (Res Gestae 9).

The Arval records preserve vows for the well-being of the emperor,modelled on those undertaken for the state on January 1^st, conducted annually on January 3^rd from at least 28 CE onwards. Literary sources verify that the January 3^rd votawere conducted throughout the empire (Tacitus, Agricola 21, Pliny, Letters 10.35-36, 100-102).

These rituals did not just ask for the safety of the emperor, but also of certain members of his family. Under Tiberius, Livia and the sons and grandsons of their household were included in the votain some years. In 38 CE, Caligular’s sisters may have been included alongside him, for although only his generic domusis not mentioned in the rite conducted on the Capitol on January 3^rd 38 CE, a subsidiary rite appears to have been conducted on January 11^th when the brothers sacrificed a cow to Dea Dia, vowed on January 3^rd, to ensure the luck and prosperity of Caligula and his sisters. Cassius Dio also says that Caligula’s sisters were included in the prayers conducted annually by the magistrates for his safety (59.3). Only fragmentary evidence survives from Claudius’ reign, but under Nero, his wife Octavia was certainly included in the vota before her death, and his other wives probably later.

Sacrificial Pantheon

The pantheon of deities that received sacrifices for the health, well-being, and prosperity remained consistent over time, but grew. As already stated, initially birthday sacrifices were conducted just to Rome’s principal state god Jupiter, but this was later expanded to the Capitoline Triad, including Juno Regina and Minerva. They were joined by personifications of divine elements considered relevant, such as Salus. Many of these goddesses were regularly worshipped in Rome and had their own temples.

These traditional gods were joined by deified members of the imperial family, the divi. Only Divus Augustus was included consistently. Divus Julius (Julius Caesar), Diva Drusilla, Diva Augusta (Livia), and Divus Claudius appeared and disappeared over time. The Genius of the emperor was also consistently included from at least the reign of Nero. This was in imitation of Rome’s domestic household cults, in which the Genius of the paterfamilias received sacrifices. We have already seen that the emperor was imagined as the paterfamilias of the state as pater patriae. Under Nero, we also sometimes see the Junones, the female equivalent of the Genius, of his wife and daughter included.

isdem [co(n)s(ulibus)] / IV Idus […] / magisterio Q(uinti) Tilli Sassi c[ollegi(i) Fratrum] / Arvalium nomine im[molavit in Capito]/lio A(ulus) Vitellius ob adv[entum Neronis Claudi] / Caesaris Augusti G[ermanici et Poppaeae] / Augustae et Claud[iae Augustae Iovi b(ovem) m(arem)] / Iunoni vacc(am) Min[ervae vacc(am) Saluti pu]/blicae vaccam [Felicitati(?) vaccam] / Spei vacc(am) Gen[io ipsius taurum Iunoni] / Poppaeae Aug[ustae vaccam Iunoni Claudiae] / Augustae v[accam] / in collegio a[dfuerunt A(ulus) Vitellius Sulpicius] / Camerin[us 3 L(ucius) Vitel]/lius C(aius) Pis[o].

When the same men were consuls, four days before the ides of… when Quintus Tillius Sassius was president of the college of Arval Brothers, Aulus Vitellius sacrificed on the Capitol in their name on account of the return of Nero Claudius Caesar Augustus Germanicus, Poppaea Augusta and Claudia Augusta, an ox to Jupiter, a cow to Juno, a cow to Minerva, a cow to Salus Publica, a cow to Felicitas, a cow to Spes, a bull to the Genius of Nero, a cow to the Juno of Poppaea Augusta and a cow to the Juno of Claudia Augusta. Present from the college were Aulus Vitellius, Sulpicius Camerinus… Lucius Vitellius and Gaius Piso.