In October of AD 37, Gaius Caesar Augustus Germanicus fell ill. He was often known by his nickname "Caligula" ("Little Booties") during his youth growing up on campaign in his own military uniform. As Tiberius sought to continue Roman stability, he determined that Gaius would be, so at age 25 he came to be emperor. Only a few months later, fever plagued him. The illness stretched into weeks, and the Roman public became frantic. After the heavy taxes of Augustus and the strict rule of Tiberius, Caligula's first months had been a godsend. Since being ratified by the Senate in March, Caligula had overturned many of Tiberius's harsh legal decisions, given 75 sesterces to each citizen (~$450 today), doubled the bonuses to the praetorian guard to 1000 sesterces, and overseen weeks of feasts and games with over 160,000 animal sacrifices. Some questioned how benevolent he truly was as Caligula had ensured Tiberius's will was destroyed and purged Gemellus, whom Tiberius had listed as co-heir, along with all of his supporters. The public, however, loved him and feared losing him.
Crowds thronged outside the gates of the imperial palace, and many held placards asking the gods to take their own lives instead of Caligula's. Sacrifices to the massive pantheon of the Roman gods did not seem to make Caligula any better. Others sacrificed to foreign gods, such as one Caligula had come to known while living in Syria: Mithras with his cult popular among the soldiers. Rumors had reached Rome of another miraculous figure in the east, a Jewish man who had not only healed and resurrected others but resurrected himself three days after being executed by crucifixion. In desperation, people became willing to try anything.
The palace doctors sent for Pontius Pilatus, the former governor of Judea who had been recalled to Rome near the end of Tiberius's rule for judgement on excessive force when executing Samaritans seeking artifacts of Moses. Tiberius had died before Pilatus arrived back in Rome, leaving his fate in legal limbo. Pilatus was eager to please the court, and he confirmed meeting the man (who was actually from Galilee and technically out of his jurisdiction), allowing the execution anyway, and witnessing the strange events afterward including an earthquake and a lengthy eclipse. He said that there was great contention among the Jewish people that the body may have been stolen while others say he had resurrected and toured the countryside for weeks until ascending into heaven itself while dozens or hundreds watched.
The palace then sent for Jewish leaders from the numerous synagogues in Rome, which had been established through diplomacy since the days of the Maccabees and Republic. Although the Jewish community in Rome had been favored by Julius Caesar, their position had struggled under Tiberius. Leaders were nervous, since they wanted to be popular with Caligula but they did not want to confirm the radical group that had followed this Jesus of Nazareth. Eventually a Christian Jew (as the Greeks used the term "Christos" rather than the Hebrew "Messiah") named Aquila was found, and he preached over Caligula's sickbed.
Approximately at that time in November of AD 37, Caligula began to recover. As he came out of his stupors, he embraced the new religion fervently, especially the rituals of baptism and communion. His practice then became more and more extreme. Caligula drank heavily and argued bitterly with anyone who suggested he stop, pointing that it was the blood of a god. Critiques from Aquila and his wife Priscilla, who had become court favorites, caused them to be banished from Rome as Caligula began to rewrite the rites for his own preferences.
Caligula sent for delegations from Jerusalem, which included Simon Peter and others of Jesus's original disciples. Their message calmed Caligula's madcap twists for a time, but ultimately he would break with the core of the church to develop his own rituals including cannibalism and partial-drowning. Numerous Romans seeking political favor joined his cult, keeping most of their actions as mysteries, while the major temples in Rome were shuttered. Caligula dispatched armed "missionaries" to close other religious centers, such as the famed Temple of Diana ("Artemis" in Greek) at Ephesus. This crackdown spurred riots and contributed to Caligula's guard assassinating him in AD 41.
The military brought Caligula's uncle Claudius to power, and Christianity fell out of favor while Claudius restored the pantheon. Pockets of Christians survived, but they were disparate in beliefs and generally considered taboo, especially after Claudius ordered the Jewish people out of Rome. Monotheism was seen as the strange philosophy of an esoteric ruler, which historians compare with the Egyptian pharaoh Akhenaten's founding of Atenism. Instead, Rome continued its pantheistic growth, adding gods collected as new realms became part of the empire. Many gods became syncretized with existing gods, such as principles of Isis being adapted to Venus and Mithras to Hercules. Jupiter remained supreme, eventually blending with Odin as Germanic peoples conquered Rome from the north.
Yet Christianity continued as a religion of the downcast, slaves, and women, teaching that in the next life "the first shall be last, and the last shall be first." Its modern form of humility is a far from Caligula's passions of prosperity and mysticism.
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In reality, Caligula recovered. Historians debate what the illness may have been, whether epilepsy, lead poisoning, encephalitis, or something else. Some scholars even question the illness as one of many legends about the short-lived emperor along with numerous other incidents that may have been taken out of context or even completely fictitious. The story could have been used by those who embraced Caligula's early months as emperor with reforms while distancing them from other legendary acts of cruelty. One legend is that Caligula ordered the executions of those who had offered their lives in sacrifice for his own so that the gods would be appeased, just in case.