Introduction

The development of Christian theology was neither immediate nor uniform. In the first four centuries, Christianity was characterised by a striking diversity of belief, practice, and interpretation. The doctrine of the Trinity, which would later become central to orthodox Christianity, was only formally defined at the Council of Nicaea in 325 CE and expanded at Constantinople in 381 CE.

Before and after these events, several Christian sects rejected trinitarian formulations and offered alternative interpretations of Jesus and God. This essay examines the original non-trinitarian sects within Christianity using only evidence from archaeology, textual sources, and historical records.

 

1. Jewish-Christian Sects

The earliest followers of Jesus were Jewish and saw him within the framework of Jewish messianic expectation. Archaeological remains of Judeo-Christian synagogues and inscriptions, along with patristic writings, confirm the existence of these groups.

• Ebionites: According to Irenaeus (Against Heresies, c. 180 CE) and Epiphanius (Panarion, 4th c.), the Ebionites held that Jesus was fully human, born of Mary and Joseph, and chosen by God at baptism. They rejected Paul’s letters and continued to observe Jewish law. Their gospel, now lost, is known through fragments cited by the Fathers.

• Nazarenes: Closely related to the Ebionites, the Nazarenes likewise maintained Jewish observances but may have accepted the virgin birth. They are mentioned by Epiphanius as existing well into the 4th century.

These sects represent the earliest strand of Christianity, rooted in Jewish tradition and without any trinitarian theology.

 

2. Adoptionists and the Shepherd of Hermas

Another early strand of non-trinitarian belief was Adoptionism, the teaching that Jesus was an ordinary man adopted as God’s Son at baptism.

• Theodotus of Byzantium (late 2nd c.) promoted this teaching in Rome.

• The Shepherd of Hermas, a Christian text from the mid-2nd century discovered in papyrus fragments, reflects a similar concept: it depicts Jesus as a man filled with the Spirit of God and chosen for divine mission, not as an eternal divine being.

 

3. Monarchianism

By the 2nd and 3rd centuries, debates over God’s unity intensified. Monarchianism emphasized that God was a single undivided being, and it developed in two forms:

• Dynamic Monarchianism: Figures like Paul of Samosata (3rd c., Bishop of Antioch) argued that Jesus was inspired by divine power but not pre-existent or co-eternal. Synodal records from Antioch condemn his teachings, demonstrating their historical presence.

• Modalism / Sabellianism: Attributed to Sabellius (c. 215 CE), this movement taught that the Father, Son, and Spirit were different “modes” or manifestations of one God, not distinct persons. Tertullian’s and Hippolytus’s polemical writings serve as evidence for its spread.

Both rejected the notion of three distinct divine persons.

 

4. Arianism and Its Expansion

The most influential non-trinitarian movement was Arianism, initiated by Arius of Alexandria (c. 256–336 CE). Arius taught that the Son was created by the Father and was not co-eternal or equal in essence.

• Textual evidence: Surviving letters of Arius, council decrees, and extensive writings of Athanasius (his opponent) preserve Arian thought.

• Archaeological evidence: Arian basilicas, especially in Ravenna, Italy, testify to the long influence of this theology among the Goths and Vandals, who maintained Arian Christianity into the 6th and 7th centuries.

Though condemned at Nicaea, Arianism shaped Christian history for centuries, proving that non-trinitarian belief was not peripheral but mainstream in many regions.

 

5. Photinians and Later Non-Trinitarian Groups

Other groups continued to reject trinitarian formulas in the 4th century:

• Photinians: Followers of Photinus of Sirmium, who emphasised Jesus’ humanity and denied his pre-existence. He was condemned at synods in the mid-4th century.

• These groups, though less enduring than Arianism, reveal the persistence of anti-trinitarian sentiment even after imperial attempts to impose orthodoxy.

 

Archaeological and Textual Anchors

The evidence for these sects comes from a mixture of sources:

• Texts: Writings of Church Fathers (Irenaeus, Tertullian, Athanasius), synodal decrees, and heresiological catalogues (Epiphanius).

• Archaeology: Inscriptions mentioning Jewish-Christian communities, papyrus fragments (e.g., the Shepherd of Hermas), and physical churches linked to Arian Christians in Europe.
  Together, they confirm that non-trinitarian Christianity was not marginal but a significant part of early Christian diversity.

 

Conclusion

The doctrine of the Trinity, now central to mainstream Christianity, was the product of centuries of debate, controversy, and imperial enforcement.

Before its formalisation, Christianity included a wide array of non-trinitarian sects: Ebionites, Nazarenes, Adoptionists, Monarchians, Sabellians, Arians, Photinians, and others. These groups, attested by both texts and material remains, demonstrate that the earliest Christian movement was theologically fluid and contested.

Far from being a settled belief, the nature of Christ and his relation to God was the central controversy of the first four centuries, and non-trinitarian voices were often the majority before their eventual suppression.