Probably the most notorious incident from Caligula’s reign is the bridge of boats that was built across the Bay of Naples from Puteoli to Baiae, a distance of more than three miles. It is not possible to date the building of the bridge precisely; Dio put the event in 39, prior to the emperor’s departure for Germany. The boats needed for the bridge were built on the spot with additional boats brought in from elsewhere (Sen. On the Shortness of LIfe 18.5; AJ 19.5-6; Cal. 19,32.1; Dio 59.17; Vict. Epit. 3.9). The boats were anchored in a double line and earth was heaped upon them to create a road in the manner of the via Appia. Dio claims the bridge was meant to be more than a simple passage over the bay and had resting places along it where fresh drinking water could be found.

On the day after the bridge was completed, Caligula, decked out in a purple cloak decorated with gold and gems, put on what he claimed was Alexander’s breastplate. Wearing an oak garland and armed with sword and shield, he sacrificed to several gods, among them Neptune and Envy. He entered the bridge on horseback from the Baiae end and charged, full tilt, down the road leading a train of infantry and cavalry. Suetonius identifies the soldiers as Praetorians and says these exercises lasted for two days. Dio says Caligula waited at Puteoli, as if resting from battle, until the exercises were completed when he returned to Baiae.

Both Suetonius and Dio say that a spectacle was reserved for the second day. Caligula drove a chariot of racehorses followed by a train of spoils and hostages, including Darius, son of Artabanus. His retinue consisted of friends and associates, the Praetorians and the general public. Dio says Caligula climbed atop a platform at the center of the bridge to harangue the crowd, contrasting his great exploit with Xerxes’ crossing of the Hellespont, pointing out that he had bridged a far wider gap. He congratulated the troops, distributed money and ordered a celebration, which lasted for the remainder of the day and well into the night. When the light faded, torches were placed on the bridge and nearby boats. People were invited from the shore to join the festivities. Unfortunately, things got out of hand. During the drunken revelry, some of the celebrants were thrown into the sea, perhaps getting caught up in a mock sea battle, and drowned. Dio says that Caligula deliberately chucked people into the sea, which was fortunately calm. [1]

Dio saw in the bridge activities a parody of a military expedition followed by a triumph. Josephus and Seneca cite this incident as an example of Caligula’s madness: Josephus claimed Caligula found it tedious to cross the bay in a trireme while Seneca thought the episode an attempt to outdo Xerxes. Suetonius, on the other hand, groups the bridge episode among Caligula’s good deeds and postulates three theories as to why the emperor built the bridge: first, he was trying to outdo Xerxes, he was attempting to inspire fear among the Britons and Germans or he was trying to confound the prediction of Thrasyllus, who said Caligula had as much chance of becoming emperor as he had of riding over the gulf of Baiae.

The explanation offered by the sources fall flat. If Caligula wanted to dispute a prediction, why not cross the bridge alone instead of with an army? Also, Caligula had been emperor for over two years prior to the events at Baiae and had no need to disprove any prediction concerning his becoming emperor. It is doubtful that word of the construction of the bridge would cause much fear in distant Germany or Britain. The Romans would certainly have recognized the connection to Xerxes. The appearance of the hostage Darius in a triumphal chariot with Caligula, posing as Alexander, turns the spectacle into a fanciful "what if" the Greek king had captured the king of Persia. The triumphal dress worn by Caligula was the same he wore when he brought back the remains of his mother and brother and what he wore when dedicating the temple of Divus Augustus (Dio 59.3.5, 7.1).

The reason why Caligula staged what in all likelihood was a military exercise was to create a closer bond with his soldiers. The building of the bridge followed his falling out with the Senate and the replacement of the consuls in September 39. It was a demonstration of his ability to command his army and show off this support before the Senate. Following the triumph at Baiae, the emperor hastened north to deal with the conspiracy of Gaetulicus, and then proceeded to Germany. [2]

The Conspiracy of Gaetulicus

In 39, Caligula departed for the north to participate in military campaigns against Britain and Germany. By October 27, news of Gaetulicus’ execution had reached Rome. The time of Caligula’s departure is not known for certain but must have occurred following his appointment of new consuls in early September. Caligula was not in Rome when he began his journey north: Dio says he was in a suburb of Rome and Suetonius places him at Mevania on the river Clitumnus, 100 miles north of the city. Caligula journeyed north in haste, and it may have been to improve his speed that he ordered villages along his route to sweep and water the streets to hold down the dust (Cal. 43; Dio 59.21.2-3). According to Suetonius, comfort was not sacrificed; eight bearers carried Caligula in a sedan chair (octaphorus). The use of this conveyance smacked of oriental luxury and was an inappropriate way for an emperor to be transported in Rome let alone in the field (Martial Epigrams 6.8). The speed at which the emperor traveled indicates urgency but not that he wanted to surprise Gaetulicus. It would have been impossible for Caligula to hide his movements because the imperial party traveled with enough supplies to be gone for six months. Actors, gladiators, his favorite horses and women along with a portion of the Praetorian Guard (Cal. 43) supposedly accompanied him.

Gaetulicus was a poet of distinction and wrote verses to curry favor with Caligula. However, he was lax with his legions, being more interested in keeping their loyalty than maintaining their fighting shape (Ann. 6.30; Tib. 41, Gal. 6.3). His level of incompetence made it only natural that a reliable commander should replace him. Gaetulicus became legate of Upper Germany in 29 with four legions under his command (Dio 59.18.4-5). His father-in-law, Lucius Apronius, was legate of Lower Germany, and Gaetulicus’ influence may have extended to his four legions (Ann. 6.30.3). Details of Gaetulicus’ fall are shadowy: Dio only says that Gaetulicus was popular with his troops, while Suetonius makes no references to the governor in his life of Caligula. Gaetulicus is mentioned in the life of Galba as the easygoing predecessor of the future emperor in Germany (Dio 59. 22.5; Gal. 6.2). The Arval record of Gaetulicus’ death mentions he died because of wicked plots (AFA xlix 6-8). The assumption is that Gaetulicus was executed at his headquarters at Mainz, although the governor could have been arrested elsewhere, perhaps on route to meet with Caligula. Certainly, Gaetulicus would not have willingly exposed himself to capture. It is more likely that agents, probably under the command of Galba, were sent to arrest the governor and execute him. [3]

The most interesting aspect of the conspiracy is the association of Gaetulicus and Lepidus. Dio says Lepidus had affairs with Caligula’s sisters, Agrippina and Livilla, and Suetonius mentions that the emperor had letters that proved their adultery and involvement in the plot. Both authors corroborate their involvement by reporting that Caligula sent three daggers to the Temple of Mars Ultor in Rome after the suppression of the conspiracy. Lepidus was executed, according to Seneca by having his throat cut by a tribune named Dexter. In a bizarre twist on his mother’s journey to Rome (carrying the ashes of his father), Caligula had Agrippina carry the bones of Lepidus to the city. On her arrival, the bones were not afforded burial but were cast out, on the motion of Vespasian in the Senate. Agrippina and Livilla were exiled to the Pontian islands and their furniture was sold by Caligula who also plagued them with threatening messages (Sen. Ep. 4.7; Cal. 24.3, 29.2; Dio 59.22.6-8; Vesp. 2.3).

The circumstances surrounding the death of Lepidus are mysterious. It is assumed that he and Caligula’s sisters were traveling with the emperor to Germany, although this is only suggested from the sources. Caligula was at Mevania prior to his journey north, a more suitable location for a confrontation with Lepidus and fitting better for Agrippina’s starting point for her journey to Rome. Dexter could have been a member of the Praetorian Guard instead of attached to a legion. The sale of his sister’s property took place in Gaul, so it has been thought they had taken some of their belongings with them, but it is more likely that Caligula sent for them to be included in his auctions of imperial property.

What drove Lepidus to conspire against Caligula was pure ambition. The death of Drusilla had been a set back for him but Lepidus remained close to the emperor, as his intervention on behalf of Flaccus indicates. Caligula’s illness creates the impression that he may have been sickly which perhaps fueled hopes in Lepidus that in the event of the emperor’s death he could assume power. Also, until the middle of 39 Caligula had not produced a child. The only other contenders from the imperial family were Claudius and more remote relatives. Lepidus’ lack of a link to the imperial family would have hampered his chances of succeeding Caligula; to overcome this obstacle he sought a connection with one of Caligula’s surviving sisters. The poet Namatianus says Lepidus "paid the penalty for foul adultery" (1.303). The younger Agrippina, whose ambitious nature matched her mother, is said by Tacitus to have committed adultery with Lepidus in the hope of power (Ann. 14.2.4). Her son, Nero (born in 37), would in her eyes be the prospective heir after Drusilla. Agrippina’s husband, Gnaeus Domitius Ahenobarbus, was ill and would die in 40 of dropsy: marriage with Lepidus would place her in a good position to secure her son in the succession. Agrippina had asked her brother to name her new son in December 37, probably hoping the he would be marked as a possible heir. Caligula had other notions and suggested the baby be called Claudius, as he looked at his uncle (Nero 6.2). With this avenue closed, Lepidus took on greater potential. He is said to have engaged in a complex triangle with both Agrippina and Livilla, most remarkably being able to keep each in the dark. Perhaps most interesting of all is that both husbands, Ahenobarbus and Vinicius, emerged unscathed from the conspiracy.

No plot could hope for success without military co-operation. Lepidus would have sought out a commander who could provide backing for his scheme. Gaetulicus may have felt threatened because of his links with Sejanus and his reputation as a lax disciplinarian who courted the loyalty of his troops. Dio and Suetonius provide no link between Lepidus and Gaetulicus, so while they may have been plotting against Caligula they had to act through intermediaries. Seneca was suspected by Caligula of being involved in the conspiracy, but his direct participation could not be proved. At the least, Seneca had knowledge of the plot since he was close to those who were implicated. His involvement becomes clear from his trial and exile in 41 under Claudius. Dio claims that Seneca plead a case too well before Caligula and was condemned to death but spared when the emperor was told by an unidentified woman that the philosopher had an advanced case of consumption (59.19.7-8, 60.8.5, 61.12.1). A miraculous reprieve is standard for those who served an emperor but later wanted to appear to have been under threat. [4]

Mauretania

Dio informs us that in 40, Ptolemy, Caligula’s cousin, the ruler of Mauretania, was murdered by the emperor (59.25.1). The date is supported by epigraphic and numismatic evidence (Ptolemy’s coinages ceased in his year 20). He was the only client-king executed by Caligula. Ptolemy was the son of Juba II and Cleopatra Selene, daughter of Marc Antony and Cleopatra. We are told Ptolemy was invited to Rome by Caligula, where he was received with honors, but was executed because he had drawn more attention on entering a theater, wearing a purple cloak, than Caligula. Presumably, Ptolemy came to Rome when Caligula had returned from Germany and was imprisoned and executed sometime during 40 (Cal. 26.1, 35.1). Seneca claims to have seen the king while in prison (Tranq. 11.12).

Ptolemy was an ineffectual king, and when his subjects rose in rebellion against the despotic behavior of his court favorites they were crushed but only with the help of Rome. Ptolemy was well treated by Rome and was given the traditional gifts given to kings of an ivory scepter and toga pica, a purple toga decorated with gold stars. The scepter figures on his coinage (Ann. 4.23- 26). After Ptolemy’s death, Mauretania was made a province and a rebellion immediately flared up. Dio suggests it was his wealth that was the motive (59.25.1). The toga-in-the-theater incident does not explain the reason why Caligula had his cousin killed. Being a king, Ptolemy was entitled to wear a purple cloak, all the more since he was related to the imperial family (AJ. 18.191, 195). It is possible that Ptolemy was involved in Gaetulicus’ conspiracy. Gaetulicus’ father had campaigned with Juba II and such an association may have induced the king to support the plot (Gal. 6,7.1; Dio 60.8.7). However, the paucity of evidence makes the entire affair a mystery.

Germany and Britain

Conquest was expected in an emperor, so Caligula set his sites to Rome’s northern borders in his quest for personal glory and expansion of the empire. Tiberius had followed a policy of restraint on the Roman frontiers causing no little impatience on the part of the Romans for military glory. Caligula probably shared this feeling and decided to take up the expansion of the empire into Britain. This would win enormous prestige for himself and even surpass the military feats of Julius Caesar and Germanicus. Trade with the British had been established during Augustus’ reign and increased over the years. The princeps contemplated an invasion of the island but was occupied by his expansion into Germany, until the disaster at the Teutoburg Forest. Strabo comments that the Romans did not consider Britain worth the effort of an invasion (2.5.8, 4.5.3).

Sources depict Caligula’s expedition as a whim, a spur of the moment decision. However, the seriousness of his intentions comes through in his extensive preparations. Suetonius says he drew levies and brought together an enormous amount of supplies. His forces were drawn from all the provinces and Dio puts their number at 200,000 to 250,000 troops. If Caligula’s preparations were similar to Claudius’ later invasion of England he would allow no fewer than three legions for the job. However, such large numbers of soldiers could not be removed from the Rhine defenses without risk, so he probably raised new legions. Historians have suggested that the legions raised by Caligula were XV and XXII Primigentae. Literary evidence for the existence of these legions is first attested in 69 CE, with the XXII located in the upper Rhine and XV in the lower Rhine. Epigraphic evidence indicates these legions were created by the Julio-Claudians and they did not exist in 23 CE (Hist. 1.55). [5]  Suetonius says that Galba, following his selection to take Gaetulicus’ command, was occupied training recruits, which could be Caligula’s new legions (Galb. 6.3).

Dio is lukewarm about a serious military operation but Philo says the Jews sacrificed for the hope of a victory in Germany (Dio 59.21.1-2; Leg. 356). In order to invade Britain Caligula needed to secure the German frontier. The condition of the Rhine legions was deplorable following Gaetulicus’ execution. To remedy the situation, a disciplinarian was called for: Servius Sulpicius Galba. Galba was an experienced soldier whom Caligula could trust to restore the efficiency of the troops. The new governor issued minute instructions to the soldiers to regulate their conduct, even to not applauding at festivals. Centurions who were too old, were ill, or were not up to commanding soldiers were dismissed. Many unsatisfactory soldiers were discharged, receiving only half the normal pension amount. The best evidence of the change that took place is brought home in the line, disce miles militare, Galba est non Gaetulicus (learn to be a soldier, soldier, don’t make a fuss, Galba’s here, not Gaetulicus) (Cal. 44.1,Galb. 6.2-3).

The primary concern of Galba was to restore discipline to the army, not participate in an invasion. The only military action he allowed were limited engagements with tribes to deter them from crossing the frontier and dealing with those tribes that had made inroads into Gaul (Galb. 6.3; Dio 59.22.2). Dio claims the Romans went a little beyond the Rhine while Eutropius says the soldiers entered Suebia (Galb. 6.3; Eutrop.7.12.2; Dio 59.21.3). Galba’s main concern was probably the Chatti, who were the focus of subsequent campaigns and an ultimate victory in 41.

How much of a role Caligula had in the campaign is confusing. He left Italy in the autumn of 39 and spent some months at Lyon, apparently staying there until Galba had everything under control. At Lyon, Caligula is said to have organized an oratorical competition, perhaps for the writing of a panegyric, where the losers had to erase their entries with their tongues or be beaten with rods and thrown into the Rhone (Cal. 20). The bizarre alternative choices of punishment make it seem that this episode was more like horseplay. Clearly, the emperor desired to humiliate those competitors that did not meet his expectations. Dio says that Caligula spent most of his time gambling and executing wealthy Gauls to get their money (59.22.3-4). One man named in the text, Julius Sacerdos, was executed without possessing any wealth. The name "Julius" suggests Caligula’s victim may have been an imperial freedman, and his execution at Lyon may indicate he had a part in Gaetulicus’ conspiracy. Such a connection to the imperial household would further underscore the danger Caligula faced but evidence is lacking. In spite of Dio’s claim, Caligula had no difficulty getting money from the provincials by non-lethal means. The Gauls were eager to ingratiate themselves with the emperor and paid large sums of money just for a dinner invitation. They also bid extravagantly on items Caligula auctioned off that had an imperial connection (Cal. 39.2; Dio 59.21.5-6). He had items transported from the old imperial residence commandeering any cart that could be found, we are told, and caused a bread shortage from lack of transportation.

While he was on campaign, the emperor conducted business as usual and kept a regular correspondence with Rome. Agrippa and Antiochus paid a visit to the court, something that disturbed the locals who feared their influence (Dio 59.24.1). A delegation of senators, led by Claudius, arrived to congratulate the emperor on escaping the plot against his life and to inform him he had been granted an ovation (Cal. 24.3, 39.1, Claud. 9.1;Dio 59.23.2; Gell. 5.6.21). Caligula was paranoid over the risk of conspiracy and refused to see some members of the delegation. The inclusion of his uncle also upset Caligula and he claimed he was insulted and did not need a guardian. His recent experience with his sisters had soured him to members of his family. According to Suetonius, there was a claim that Claudius had been thrown into a river fully clothed, but this may be confusion over the losers of the literary contest. Claudius’ presence in Lyon is attested at the dedication of a building from an inscription (AE 1980.638) with Caligula and a female. She is taken to be Caesonia, who may have been in Gaul with the emperor prior to his departure for Germany (Claud. 9.1). [6]

In January 40, Caligula assumed his third consulship alone, his colleague having died before assuming office (Cal. 17.1; Dio 59.24). At some point early in the year he journeyed to the German frontier, probably arriving at Mainz, where Galba’s troops made a good impression on him and were awarded commendations (Galb. 6.3). Caligula’s military activities in Germany are garbled at best. Suetonius says he went across the Rhine with a detachment of his bodyguard but he saw no action. As a consequence of this activity, the emperor created a new crown for the soldiers call the coronae exploratoriae or scouting crown. Suetonius also relates that the emperor found himself in a narrow pass on the wrong side of the Rhine and when approached by enemy soldiers fled in a panic. Dio says Caligula was acclaimed imperator seven times in Germany without winning a battle or killing any of the enemy. However, he contradicts himself later when Dio reports Claudius was hailed imperator several times for which there was no prescendent (Cal. 45.1-2, 51.2-3; Dio 59.22.2, 60.21.4). It was considered appropriate for emperors to claim credit for the victories of their subordinates. When Caligula sent a laurel wreath to Rome to mark the defeat of German youths his claims may not have been for a personal victory, but he probably exaggerated his own exposure to danger. The Senate did nothing to discourage such claims. Vespasian proposed special games for the victory of Caligula, and there were celebrations in other parts of the empire (Cal. 45.3, Vesp. 3.3; Persius Satires 6.43-4).

Caligula is supposed to have proceeded, during February or March 40, with his invasion of Britain, immediately following operations against the Germans. Dio’s narrative breaks off at this point and when his account picks up, the emperor is already on the shore of the English Channel. What exactly happened has been a hot topic of scholarly debate. After Caligula had drawn up his soldiers in battle line, along with ballistae and siege equipment, he went out to sea in a trireme and sailed back. He next sat on a high platform and gave the battle signal, ordering his soldiers to gather conchas (seashells) in their helmets and the folds of their tunics as spoils of the Ocean. He sent the shells to Rome to be exhibited as booty (Dio 59.25.1-3; Cal. 44-7; De Caes. 3.11-12). The debate concerning this incident centers on whether the emperor actually ordered his troops to collect shells or the tradition behind the incident was corrupted over time, so we do not know what the emperor meant.

Travel over the channel was closed to ship traffic until March and considered unsafe until May, so it is unlikely an expedition could have been completed (Cal. 49.1; Vegestius 4.39). Caligula was no lover of travel by sea and would hardly want to risk a storm on the channel (Cal. 45.2). Suetonius also reports that Caligula constructed a lighthouse as a monument to his victory at Gesoriacum (Boulogne) which was intended to aid ships in ferrying men and supplies to Britain. If this sequence is correct, then Suetonius implies the invasion was meant for a later date (Cal. 46). So, what happened on the English Channel?

There are various scenarios put forward by scholars. One suggests there may have been military action against the Canninefactes. However, the victory over Oceanus that was claimed by Caligula is hardly explained by a land victory. Another idea is that there was no military campaign but only maneuvers along the channel coast. This does not explain why shells were collected, since they had no value as missiles. Another explanation suggests substituting the word musculi for concha, so that the soldiers were collecting sapper’s huts and not shells. Yet, another view places this event not on the English Channel but on the Rhine in lower Germany. [7]

The word Caligula used was concha, which has various meanings in Latin: a type of shellfish, parts of mollusk or shellfish or an object with a shell-like cavity. Concha has been used as a slang word for female genitalia, from which the conclusion arose that Caligula might be inviting his soldiers to a brothel! What Caligula was possibly referring to with the word concha was a small, fragile boat, which is sometimes called a "cockle." (For example, in Caesar and Cleopatra by George Bernard Shaw, Apollodorus (Act 3) refers to his boat as a "poor little cockleshell") The emperor, therefore, was ordering his soldiers to collect some British boats that had been captured in the English Channel. In line with this conclusion, the ballistas and other artillery that was arrayed on the shore were not siege engines but catapults and other devices that were also used in naval warfare. [8] Troops would not be in battle line formation if there were about to board ships for an invasion. The Roman fleet had been pulled over the tidal line for safekeeping, so the equipment on board would have been removed to facilitate hauling the triremes on shore. Suetonius mentions that Caligula had the triremes carried overland to Rome (Cal. 47). The purpose in this was to parade the ships in the emperor’s triumph. If the victorious ship were to be displayed, why not some of the captured British boats? In the end, Caligula canceled his triumph since this minor action was a merely a prelude to his true invasion of Britain. [9]

It is unlikely that an invasion was contemplated at this time, particularly since the German frontier was not secure. Galba continued his campaigns until 41 brought an overwhelming victory over the Chatti and Publius Gabinus was victorious over the Cauchi (Dio 60.8.7). Caligula’s own words on this affair, quoting Aeneas (Aen. 1.207) who was rallying his men when their fortunes were low, "Bear up, and preserve yourselves for better times!" indicates he was not in a position to mount and invasion (Cal. 45.2). No mention is made in the sources of the enormous amount of transport ships that would be necessary to ferry troops to Britain.

In a different context, Suetonius mentions that Caligula’s only accomplishment in the north was to receive the surrender of Adminius, son of Cunobelinus. An anti-Roman faction or perhaps his father had driven Adminius out of Britain possibly (Cal. 44). He may have sought refuge with Caligula while he was at the channel although Suetonius does not directly link Adminius with the events that took place there. He is not mentioned in the epitome of Dio but the 5th century writer Orosius connects him to the channel events. Orosius says Caligula came north with a large force, scouring Germany and Gaul, and stopping at the edge of the Ocean in view of Britain. There, he received the surrender of Adminius and returned to Rome due to a deficiency of war materials (Histories against the Pagans 7.5.5). Tacitus remarks that Caligula’s campaign fell through because of his own fickle nature and because his campaign in Germany was not a success (Agr. 13.4).

Caligula faced the prospect of loss of face if he returned to Rome without something to show for his expedition. Adminius gave him the opportunity of salvaging the situation. The surrender could have been staged amid military pomp. After the campaign, Caligula gave a gift to his soldiers of 100 denarii, a modest sum for a major campaign but suitable for a ceremonial occasion (Cal. 46). The submission of Adminius may have taken place at sea, which would explain why Caligula sailed out in a trireme and, significantly, the emperor ordered the ship brought to Rome as part of his planed triumph. Suetonius mentions a lofty message Caligula sent to the Senate, the wording suggesting the "whole island had been handed over." The letter was to be read when the Senate gathered at the Temple of Mars Ultor, where senators considered claims of a triumph and to where victors sent their triumphal insignia (Cal. 47, 48.2). However, Suetonius says that Caligula planned a triumph but accepted an ovation to celebrate a victory over the conspiracy. The decision may well have been his own rather than the Senate cheating him out of his triumph. That Caligula did not assume the name Britannicus indicates he did not consider the military action completed.

Suetonius suggests that Caligula had a wild scheme to eliminate the legions (the 1^st and 20^th) that had taken part in the mutiny of 14. No other source records this. Although he was dissuaded from this plan, Caligula then declared he would carry out a decimation of the legions. He was at the point of carrying out his threat when he thought the troops might resist, so he turned his ferocity on the Senate instead (Cal. 48.1-2). This story sounds like a wild exaggeration. The soldiers who participated in the mutiny were probably no longer serving in the army after 25 years, their places having been taken by other men. One may ask how Caligula would manage to carry out the massacre two entire legions. However, we are told that he was only planning to do these things, so the story may have derived from a cynical remark from the emperor.

There is also a logistic problem with Caligula’s return to Rome in May. Suetonius indicates that he did not begin his return journey immediately following the British episode and implies he traveled at a leisurely pace since envoys were sent to urge his return. Caligula would have to have left the channel area by the end of March. It is not know what Caligula did on his way to Rome or where he may have stopped. He must have felt some bitterness that the military glory he had sought had slipped away. However, his hostility toward the Senate had not abated during his months of absence.