Parallel Beliefs: Mithras and Early Christianity in Rome

In the vast expanse of the Roman Empire, there was more than one belief system. It was more in-depth, layered, and eventually two salvation-focused religions emerged within the same cultural landscape: the cult of Mithras and early Christianity. But why did Christianity endure while Mithraism declined despite their similarities? 

The cult of Mithraism flourished in the Roman Empire between the 1st and 4th centuries CE. It is often linked to an older Indo-Iranian deity, Mithra, known from Zoroastrian tradition. However, modern scholarship stresses that Roman Mithraism, our main focus, was not simply imported Persian religion; instead, it appears to have been inspired by Eastern imagery, but reshaped into something distinct. 

Mithraism left no surviving sacred scripture, no theological treatises written by believers or followers, and no narrative accounts to explain doctrine or order. Modern-day knowledge comes from archaeology, as over 400 mithraea have been discovered across the Roman Empire, providing physical layouts, inscriptions, altars and imagery. Some of the inscriptions mentioned include dedications from initiates, revealing names, ranks and devotional formulas. We have also found reliefs and iconography in stone carvings of the Tauroctony and related scenes, which form the primary visual record of the belief. 

Unlike the civic Roman religion of the time, which was public and ritualised through state ceremonies, Mithraism operated in intimate and enclosed settings, small underground temples called Mithraea. Each Mithreaea typically resembled a cave, with benches along the sides of the space, and a central aisle leading to the image of Mithras killing the bull. This religion was male-only, secretive and structured around graded initiations. 

This evidence strongly suggests that Mithraism spread in close association with the Roman military, which is also supported by Beck in his research. Numerous Mithraea have been discovered in frontier zones, particularly in Britain, Germany and along the Danube river, often near military forts. At sites such as Carrawburgh on Hadrian’s Wall and the garrison town of Dura-Europos, mithraea were found in close proximity to army barracks, indicating that soldiers were among its followers. The inscriptions found in these spaces frequently record dedications by centurions and other military personnel. Although Mithraism was not limited to soldiers, its graded initiation system and emphasis on loyalty and brotherhood likely resonated within the structured and disciplined environment of army life.

At the same time, early Christianity was spreading in the urban centres across the Roman Empire. It offered salvation, ritualistic meals, baptism and the promise of eternal life through Christ. Unlike Mithraism, it gradually opened itself to all, women, slaves, elites and outsiders alike. This helped us gain insight and document clearer evidence of the aims and core beliefs of the Christian doctrine. 

Both religions existed within the same imperial framework, both addressing spiritual longing in a world of instability. They were both, to begin with, initiatory religions, requiring either graded initiations or baptism and instruction before full participation. They both placed symbolic meals at the centre of their community's identity. They both address existential concerns, such as life, death, cosmic order and redemption. 

There have been claims that Mithras was born on 25 December, that he emerged from a virgin birth or from a rock, that he had twelve disciples, and that Christianity directly copied Mithraic Eucharistic ritual. These ideas largely stem from the early twentieth-century work of Franz Cumont, which is now widely regarded as overly speculative.

But despite the similarities we might find, their structures and accessibility differed profoundly, and this is what we can see caused the eventual decline of Mithraism. 

The most commonly cited turning point took place during the reign of Emperor Constantine the Great, in the 4th century, between 306 and 336 CE. 

Constantine is one of the notable figures who was rumoured to be devoted to Mithras, alongside other Roman Emperors and rulers from the Hellenistic East. While he did not strictly follow Mithraism as a religion, he blended its imagery with the sun god, Sol Invictus, into his early rule. He used images of the sun on his coins and in his propaganda, having grown up in court around his father, Constantius Chlorus, who was also a devotee of Sol Invictus. 

However, in 312 CE, before the Battle of the Milvian Bridge, Constantine allegedly experienced a vision of an early Christian symbol, the Chi-Rho, and after his subsequent victory, converted to the Christian faith.

His conversion to this faith set the first stone to the decline of Mithraism. Following his new belief, he brought Christianity to the forefront of the Empire, but it was not yet the official religion; it was simply no longer marginal. This change granted Christianity legal status through the Edict of Milan in 313 CE. This matters as it allowed Christianity to build publicly, becoming openly organised and receiving imperial patronage. Mithraism, by contrast, remained private, local and decentralised. 

Throughout the 4th century, emperors increasingly supported Christianity. This assisted its transition from a persecuted sect to a state-supported religion. By the time of Theodosius (379 - 395 CE) Christianity had become the official state religion of the empire. Pagan practices were becoming progressively restricted, with the aid of the political suppression from Theodosius during his reign. 

Mithraism, on the other hand, lacking broad inclusivity and a strong public structure or imperial support, declined. Its temples were slowly abandoned. Its symbols faded. By the end of the century, Christianity had become the dominant religious force of the empire. A religion that operated in small underground spaces consistently struggled to compete with imperial basilicas and political manoeuvres. The intimacy and exclusivity that were once Mithraism's strength were now limiting its expansion. 

Through our archaeological exploration, we can see layers indicating that many mithraea were abandoned or filled in during the late 4th century, following the rise of followers converting to Christianity. Some were deliberately closed. Some were simply left unused. Meanwhile, Christian churches expanded both architecturally and socially. Rome's religious landscape had changed drastically. 

The journey of divergence between Mithraism and early Christianity shows that this was not a simple story about two religions competing. It reveals something more fundamental about how belief systems endure or disappear. 

The comparison reveals that symbolism alone does not determine survival. Both Mithraism and Christianity offered:

• Initiation

• Sacred meals

• Themes of salvation

• Cosmic struggle

• Strong communal identity

On the surface, they were not that different. Yet similarity did not guarantee equal futures. This suggests that ideas alone do not survive because they may be spiritually compelling. They survive through social scaling, political adaptability, demographical expansion and institutionalised authority. 

Despite the cultural changes, Mithraism stuck to its guns and kept its restricted participation to small groups of men. It did not follow Christianity's lead of welcoming women, children, slaves, and entire households!

As the Empire was structured around strong family networks, this difference was enormous. Christianity could easily spread through marriage, kinship, domestic spaces and care networks. Mithraism was limited to male social networks, such as military involvement. 

This goes to show that movements or religions that are built around open participation tend to expand rapidly, while those reliant on secrecy or niche identity often plateau unless they gain institutional backing. 

What fascinates me most about this connection is not which religion was 'truer', but the way in which Christianity became so scalable. Mithraism feels intimate, selective and almost elite with its brotherhood bound by secrecy. Before exploring these histories more, I thought that surely that type of sect would be preferable in a patriarchal empire such as Rome. But Christianity managed to unify the people with its accessibility to the potential of salvation. 

It makes me wonder whether any idea can survive, not based on how profound it may be, but how adaptable it may be to the times, culture and society it may be in. 

Even today, we see this pattern. Some movements, such as Radical Right Movements or Anti-Establishment movements, thrive on exclusivity, invite-only communities, niche ideologies, and closed networks. Others, like the Trans Rights Movement and the Slow Movement (big fan), are open to the masses and are growing rapidly, even if that growth potentially dilutes their original intensity. 

This view makes me feel like the parallel beliefs between Mithraism and Christianity were not necessarily spiritual or in direct competition with each other, and perhaps they could have thrived alongside each other given equal levels of imperial support. But one remained a closed circle and was swept away as the other became a civilisation. 

Reference and Sources | YouTube, ReligionForBreakfast | Manfred Clauss, The Roman Cult of Mithras (2000) | David Ulansey, The Origins of the Mithraic Mysteries (1989) | Roger Beck, The Religion of the Mithras Cult in the Roman Empire (2006)