Roman Empire

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The Roman Empire was the imperial phase of the Roman state, conventionally dated from Augustus’s settlement of 27 BCE — when one man took permanent control of the republic’s machinery — to 476, when the last emperor in the West was deposed. At its height it ringed the Mediterranean and reached from Britain to the Euphrates, governing perhaps a fifth of the human race under a single law and a common currency.

For the religious and philosophical currents this archive gathers, the empire was less a backdrop than a precondition. Its roads, its shared Greek and Latin, and its long stretches of internal peace let texts, teachers, and cults move across distances that had never been so open. The same century that saw the empire consolidate also saw an unprecedented mingling of Egyptian, Greek, Levantine, and Persian religion in its cities. Out of that mingling came the Hermetic writings — Greek philosophical-religious treatises ascribed to an Egyptian Hermes — along with the schools later called Gnostic, the revived Platonism of Plotinus and his successors, and the small Jewish sect that became Christianity. None of these would have taken the form they did outside the conditions the empire created.

From republic to principate

The empire did not announce itself. The institutions of the Roman Republic — consuls, senate, the annual magistracies — were never formally abolished; they were quietly drained of independent power and gathered, one office at a time, into a single pair of hands. After the assassination of Julius Caesar in 44 BCE and the long civil wars that followed, Caesar’s heir Octavian emerged sole victor at Actium in 31 BCE. In 27 BCE he handed the republic back to the senate in a carefully staged act of restoration and received, in return, the name Augustus and a controlling grant of provinces and armies. The arrangement historians call the principate kept the forms of the old order while concentrating its substance; Augustus styled himself princeps, first citizen, rather than king. The reign that followed — until his death in 14 CE — fixed the shape of the imperial system and inaugurated the long internal peace, the pax Romana, under which the Mediterranean became for the first time a single connected world.

That connection is the fact most relevant to everything else on this site. A merchant, a soldier, a wandering teacher, or a sacred text could move from Alexandria to Rome to Lyon along paved roads and policed sea-lanes, in a common administrative language, under one coinage. Religions and philosophies that had been local became portable. The cult of Isis traveled from the Nile to the harbor towns of Italy and Gaul; the Hermetic dialogues composed in Greek-speaking Egypt circulated among readers who had never seen the Nile; the letters of a single tentmaker in Tarsus reached congregations from Corinth to Rome.

The state cult and the divinization of emperors

Roman religion in its public form was a religion of correct practice rather than of creed — a network of reciprocal obligation between the city and its gods, treated at length under ancient Roman religion. Onto this inherited civic cult the empire grafted something new: the worship of the ruler himself. The precedent was Julius Caesar, voted divus — a deified mortal raised among the state gods — by the senate in 42 BCE, two years after his murder; a comet that appeared during his funeral games was read as his soul ascending and named the Julian star. Augustus handled his own divinity with calculated restraint. In the Greek-speaking East, where Hellenistic kings had long received cult, provincial worship of Augustus together with the goddess Roma was organized from 29 BCE at centers such as Pergamum and Nicomedia. At Rome itself he claimed nothing openly divine while alive, permitting instead the veneration of his genius — the generative guardian-spirit of the head of a household, by which Romans swore oaths.

The distinction between genius and numen — the spirit attached to a person and the divine power present in an act — gave the cult its flexibility. A living emperor was approached through his genius and his numen; a dead one, if the senate judged him worthy, was formally consecrated by decree, his apotheosis sometimes dramatized by releasing an eagle from the funeral pyre to carry the soul upward. Consecration was thus also a verdict: a good emperor became a divus, while a hated one — Nero, Domitian in the senate’s memory — was denied the honor and his name struck from monuments. In the East the cult took root readily on the model of older ruler-worship, and cities competed for the prestige of an official imperial temple. In the western provinces, which had no native tradition of god-kings, it worked instead as an instrument of Romanization, offering provincial elites a priesthood — a flamen of the deified emperor — that paralleled the ladder of civic honors. Mark Antony had served as the first flamen of the deified Julius; two centuries later, provincial priests of the imperial cult at Lugdunum stood at the head of the Gallic provinces.

This is the hinge on which the persecution of Christians turned. The empire asked not for belief but for an act — a pinch of incense, a small sacrifice before the emperor’s image — as a token of loyalty. Under Decius in 249 every inhabitant was required to sacrifice and obtain a certificate proving it; Jews alone held a recognized exemption. Those who became Christians and refused the gesture were read not as heretics but as traitors, withholding the minimal civic act that bound the empire together. The conflict was, at root, between two incompatible accounts of where ultimate allegiance lay.

The imported cults

Roman religion was capacious and, in practice, absorptive: it identified foreign gods with its own and welcomed new ones when the welfare of the state seemed to require them. The first great import predated the empire. In 204 BCE, in the fourteenth year of the war against Hannibal, the Sibylline Books were read to counsel bringing the Great Mother of Phrygian Pessinus to Rome; the goddess arrived as a black meteoric stone, received at Ostia by the man the senate named the best in the city, and was installed in a temple on the Palatine dedicated in 191 BCE. The cult of Cybele, the Magna Mater, came with her consort Attis and her self-castrated priests, the galli, and with a festival, the Megalesia, kept each April. For centuries Roman citizens were barred from the ecstatic rites and the priesthood; only later were they admitted by way of the taurobolium, a costly bull-sacrifice that became, in the later empire, a mark of aristocratic pagan piety.

The mystery cults proper — initiatory associations whose central rites were closed to all but the sworn, surveyed under mystery religions — flourished in this open imperial frame. They differed from the public cult in kind: where civic religion asked correct performance from a whole community, the mysteries offered the individual a personal bond with a deity and, in several cases, the promise of a better lot beyond death. The oldest, the rites of Demeter and Persephone at Eleusis, drew initiates from across the empire, emperors among them, and turned not on doctrine but on something undergone — Aristotle’s formula, that the initiate comes not to learn but to be put into a state, governs the whole genre.

The cult of Isis, carried from Egypt, gave its initiates a goddess of cosmic compassion who could promise rescue from the blind turning of fortune; its processions, its sacred water drawn from the Nile, and its tonsured priests are described from the inside by Apuleius in the closing book of his Golden Ass. The Mithraic mysteries present the sharpest case of all: a men’s cult, especially strong among soldiers and officials, that met in small cave-like sanctuaries built across the empire from the second century, with a seven-grade hierarchy of initiation keyed to the seven planets and a central image — the tauroctony, the god slaying a bull — repeated in hundreds of variants while no doctrinal text from within the cult survives. Roman Mithras shares the name of the Iranian Mithra and the trappings of Persian wisdom, but the older view, owed to Franz Cumont, that the Roman cult was simply Zoroastrian religion in western dress was dismantled at the first international congress of Mithraic studies at Manchester in 1971; the dominant account now treats it as a Roman religious creation that staged Persian elements as exotic surface. Its banquet of bread and cup so resembled the Christian Eucharist that Justin Martyr, in the second century, could only explain the likeness as a demonic imitation — which is to say the two grew up side by side, drawing on a shared ritual language, rather than one copying the other.

The philosophical schools

The same conditions sustained the philosophical schools, which under the empire functioned for the educated less as academic disciplines than as ways of life with a doctrine of the soul attached. Stoicism, founded in Athens around 300 BCE, reached its most enduring voice precisely in the imperial period: the freed slave Epictetus, whose teaching survives in the Discourses transcribed by his pupil Arrian; Seneca, tutor and minister to Nero; and the emperor Marcus Aurelius, whose private Greek notebook, the Meditations, is the rarest of documents — the inner discipline of the most powerful man alive, written for no audience but himself. Stoic physics — a single rational fire, the logos, pervading and ordering the cosmos — gave the wider culture a vocabulary for an immanent divine reason that would echo through Hermetic and Christian theology alike.

The decisive philosophical event of the empire’s maturity was the revival of Platonism by Plotinus (c. 205–270), who taught at Rome in the third century and from whose lectures his pupil Porphyry assembled the Enneads. The system later called Neoplatonism reads all reality as descending from a single ineffable source, the One, through Intellect (nous) and Soul into the material world, with the soul’s true work being the ascent back toward its origin. This was philosophy that bordered on religion, and in the hands of Plotinus’s successors — Porphyry, Iamblichus, and the school at Athens down to Proclus and Damascius — it absorbed the ritual practice called theurgy, the use of sacred rites to draw the soul upward, and made common cause with the Chaldean Oracles and the older mysteries. Neoplatonism became the intellectual framework within which late pagan antiquity defended itself, and the channel through which much of the prisca theologia — the conviction of an ancient shared wisdom running from Hermes and Orpheus to Plato — would later pass into the Christian and Islamic Middle Ages.

Dreams, oracles, and the esoteric undercurrent

Beneath the public cults ran a continuous current of divination, dream-lore, and ritual technique that the empire neither created nor suppressed but allowed to circulate freely. The interpretation of dreams was a working profession with its own technical literature; the one such manual to survive whole, the Oneirocritica of Artemidorus of Daldis, compiled in the second century, sorts dreams into the merely somatic and the genuinely predictive and insists that the same image means different things for a free man and a slave, a woman and a soldier — a window onto the lived assumptions of an entire society about signs and the future. Two centuries later the Neoplatonist Macrobius gave the Latin Middle Ages its standard fivefold scheme of dreams in his commentary on Cicero’s Dream of Scipio, and the bishop-philosopher Synesius of Cyrene grounded dream-divination in the Neoplatonic doctrine of the soul’s pneumatic vehicle. The Sibylline Oracles, the hellenistic astrology inherited from Babylon and Egypt, the practice of incubation in healing sanctuaries, and the magical handbooks of Greco-Roman Egypt all belong to this stratum — the everyday machinery by which people in the empire reached past the visible toward knowledge and help.

Crisis, recovery, and the turn to one god

The third century nearly ended the experiment. After the murder of Severus Alexander by his own troops in 235, the empire entered fifty years of near-anarchy in which more than fifty men claimed the imperial title and almost every one died by violence. The provinces fractured: a breakaway Gallic empire held the West from 260, and a Palmyrene empire under the queen Zenobia held the East from the late 260s. Plague — the so-called Plague of Cyprian — ran through the cities; the silver coinage was debased until it collapsed; the long-distance trade that had carried texts and cults began to seize. Recovery came from the army. Aurelian (reigned 270–275) reunited the territory by force and, in 274, raised the cult of Sol Invictus, the Unconquered Sun, to the front rank of state religion — a single supreme solar deity behind whom the empire’s many gods could be ranged. The drift toward one god, whether read as philosophical or political, was underway before any emperor became Christian. Diocletian (acceding 284) refounded the state on a new administrative basis and shared power among four rulers, the Tetrarchy, restoring order at the price of the old principate’s fictions; his reign also produced the last and most systematic persecution of the Christians.

The Christian turn

The fourth century reversed the relation between the empire and the new faith. After Constantine’s victory in 312 and his conversion, the Edict of Milan of 313 — agreed with his eastern colleague Licinius — granted Christians legal toleration and the return of confiscated property; it did not yet make Christianity the religion of the state. That came in stages. Constantine summoned the bishops to Nicaea in 325 to settle the church’s own divisions; later in the century the short reign of Julian (361–363) attempted a deliberate pagan and Neoplatonic restoration that died with him. The decisive measure was the Edict of Thessalonica of February 380, by which Theodosius I made Nicene Christianity the official religion of the empire; in 391 and 392 a series of his edicts banned sacrifice and ordered the closing of the temples. The old cults and the philosophical schools that had sheltered the pagan inheritance were progressively closed; the eternal flame of Vesta was extinguished, the Eleusinian sanctuary fell, and in 529 the emperor Justinian closed the Neoplatonic school at Athens, sending its last masters — Damascius among them, and Simplicius — briefly into exile at the Persian court of Khosrow I before a peace treaty in 532 allowed their return. The world of the imported cults and the open schools did not end in a single act, but its public institutions were dismantled across a century and a half.

The long ending and the inheritance

Historians have long debated whether the western empire fell in 476 — when the general Odoacer deposed the boy-emperor Romulus Augustulus and sent the western regalia to Constantinople — or whether it slowly transformed into the Germanic kingdoms that had been settling within its frontiers for generations. The eastern half, governed from Constantinople and now usually called the Byzantine Empire, continued for nearly another thousand years, carrying Roman law, Greek learning, and the Neoplatonic-Christian synthesis forward until 1453. What is not in dispute is that the religious landscape the empire had made outlasted its politics. The Hermetic corpus, the Neoplatonic texts, and the Gnostic writings recovered in the modern period are all, in their origins, the sediment of this world: documents of what people in a single vast and mixed polity reached for when they reached past the visible. The empire was the crucible in which the Western esoteric inheritance was first compounded — Egyptian, Greek, Persian, and Jewish elements brought into one circulating system and held there long enough to fuse.

Texts, editions, and scholarship

The empire’s own literature on its religion survives unevenly, and the modern study of it rests on a body of editions and reconstructions that themselves have a history. For the imperial Stoics the primary texts are largely intact: George Long and the later translators rendered the Meditations of Marcus Aurelius and the Discourses of Epictetus into a standard English, and Elizabeth Carter’s eighteenth-century Epictetus remains in print; the public-domain MacKenna translation of Plotinus’s Enneads gives English readers the foundational Neoplatonic text in full (MacKenna’s Enneads; Matheson’s Discourses of Epictetus). For the mystery cults the documentation is the reverse of the philosophical case — rich in objects, mute in doctrine. The Roman cult of Mithras must be reconstructed almost entirely from its monuments; Maarten Vermaseren’s Corpus Inscriptionum et Monumentorum Religionis Mithriacae (2 vols., 1956–60) gathers the inscriptions and reliefs, while Franz Cumont’s The Mysteries of Mithra, translated by Thomas J. McCormack (Chicago: Open Court, 1903), preserves the great Iranian-continuity synthesis that dominated the field until 1971 — historically foundational, though its central thesis is no longer the consensus (https://www.gutenberg.org/ebooks/22213 hosts Cumont’s companion Oriental Religions in Roman Paganism). The modern standard is Manfred Clauss, The Roman Cult of Mithras, translated by Richard Gordon (Edinburgh University Press, 2000), with Roger Beck’s The Religion of the Mithras Cult in the Roman Empire (Oxford University Press, 2006) giving the leading current interpretation. Porphyry’s On the Cave of the Nymphs, the one surviving ancient philosophical reading of Mithraic symbolism, is available in Thomas Taylor’s 1823 Select Works of Porphyry (https://www.gutenberg.org/ebooks/77014).

For the empire as a whole, Mary Beard’s SPQR: A History of Ancient Rome (Liveright, 2015) is the accessible modern narrative, and her co-authored Religions of Rome (2 vols., Cambridge University Press, 1998) the standard account of the religious system. Peter Brown’s The World of Late Antiquity (Thames & Hudson, 1971) reframed the empire’s last centuries not as decline but as a creative transformation — the very period in which Hermetism, Neoplatonism, and Christianity took their lasting shapes. On the dream-literature, Daniel Harris-McCoy’s edition of Artemidorus, Oneirocritica: Text, Translation, and Commentary (Oxford University Press, 2012), is the fullest scholarly treatment, and the German translation of Artemidorus that Freud used — Friedrich Krauss’s Symbolik der Träume (1881) — remains the document behind the modern psychological reception of ancient dream-interpretation. The Corpus Hermeticum itself, in G. R. S. Mead’s translation, and the Sibylline Oracles in Milton Terry’s version stand here as the empire’s own surviving esoteric voices, the texts in which the mingled religion of the imperial cities speaks for itself.

→ In the library: The Corpus Hermeticum (Mead) — I. Poemandres · Terry — The Sibylline Oracles (1899) · MacKenna — Plotinus, The Enneads · Matheson — Epictetus, The Discourses

→ Related: Neoplatonism · Gnosis · Hermes Trismegistus · Dendera · Mesopotamia · Mithraic Mysteries · Mystery Religions · Isis · Stoicism · Christianity · Ancient Roman Religion · Roman Republic · Byzantine Empire