The doctrinal horizon of the Assyrian Church of the East is shaped by a distinctive East Syriac vocabulary and by the historical experience of developing theology largely outside Byzantine oversight. At the center of its self-understanding is a Christology that emphasizes the full reality of both the divine and human in the one Lord Jesus, but it formulates that confession using Syriac-language categories—terms such as qnoma and person—that do not map neatly onto Greek technical language. In the tradition’s own idiom, adherents commonly explain qnoma as an “individual reality” or concrete instance of a nature; they hold that in the one person (persone or nasikha in Syriac usage) of the incarnate Word there are two qnome (plural of qnoma), divine and human, each retaining real properties. Scholars often situate this stance within the family of dyophysite formulations, noting its historical divergence from both miaphysite constructions associated with the Oriental Orthodox and some Chalcedonian presentations that employ different Greek technical vocabulary.
The contentious label “Nestorian” requires careful handling. Western and Byzantine polemicists attached the name of Nestorius (Patriarch of Constantinople, early fifth century) to the East Syriac tradition, alleging that it divided Christ into two persons. Many modern scholars, however, argue that the East Syriac formulations are more nuanced and that the church’s theology developed independently in Mesopotamia, albeit in conversation with the controversies of the fifth and sixth centuries. The church itself tends to reject the pejorative sense of the term and points to internal authorities—such as Babai the Great (active in the late sixth and early seventh centuries), whose theological treatises defended the tradition’s language concerning Christ’s two natures, and the extensive exegetical output of the School of Nisibis—to explain and systematize its doctrine. The School of Nisibis (a major center for theological and biblical instruction located in what is now southeastern Turkey and active especially from the late antique period into the early medieval era) and related centers such as the schools in Edessa and Seleucia-Ctesiphon played formative roles in shaping the church’s theological vocabulary.
Scripture and its Syriac witness occupy a central place in doctrinal life. The Peshitta—the standard Syriac translation of the Old and New Testaments—functions as the scriptural backbone of liturgy, preaching and exegesis. Manuscripts of the Peshitta exist in monastic collections in Mesopotamia (for example, manuscripts preserved in monasteries historically located near Mosul such as Mar Mattai and Rabban Hormizd), in major Western repositories (including the British Library and the Vatican Library), and in private and national collections across the Middle East and the diaspora; extant manuscripts range in date from late antiquity through the medieval centuries. Exegetical practice in the Church of the East is historically marked by a robust patristic commentary tradition: theologians and biblical scholars in the Church produced commentaries, homilies and scholastic treatises in Syriac that shaped catechesis and pastoral care. Figures such as Ephrem the Syrian (fourth century), while not exclusively identified with the Church of the East, influenced Syriac hymnography and devotional styles; Isaac of Nineveh (seventh century) produced ascetical homilies in Syriac that remained central to spiritual formation across Syriac-speaking Christianity.
Asceticism and monastic spirituality significantly shape the church’s conception of the Christian life. The tradition venerates monastic founders and hermit-saints and has preserved monasteries that became centers of learning and pilgrimage—examples include the Monastery of Mar Mattai near Mosul and the Rabban Hormizd Monastery near Alqosh in northern Mesopotamia. The ascetical literature preserved in these milieus often articulates a spiritual anthropology that emphasizes deification or theosis in Syriac idiom: human transformation through the work of God, pursued through disciplined prayer, fasting, almsgiving and contemplative practice. Isaac of Nineveh’s Ascetical Homilies (widely read in Syriac and in later translations) are commonly cited by adherents as exemplifying a theology of inward repentance and spiritual healing.
Sacramental theology is another core locus of identity. The East Syriac liturgical tradition is structured around Eucharistic celebrations, daily offices and sacramental rites rendered in classical Syriac and in local vernaculars. The Eucharistic anaphora attributed to Addai and Mari is especially distinctive: scholars date its core to an early period, and it is commonly described by historians as among the oldest Eucharistic formularies in continuous use. In the modern ecumenical conversation, this anaphora attracted particular attention because certain early recensions do not contain an explicit verbal narrative of the Institution (the Words of Institution) as they appear in some Western rites; in 2001 the Roman Catholic Church’s Pontifical Council for Promoting Christian Unity issued findings recognizing the validity of the anaphora in the context of East Syriac tradition, a conclusion that reflected detailed liturgical and historical study and which ecumenical partners continue to discuss. The tradition teaches that the church’s sacraments—baptism, chrismation (anointing with oil), Eucharist, confession, ordination, marriage and unction—are channels through which divine grace is communicated; in many historic East Syriac practice contexts, baptism and chrismation are administered together for infants, and clergy orders (deacon, priest, bishop) follow patterns common to other Eastern churches, with episcopal office historically linked to celibate monastic candidates and parish ministry often including married presbyters.
Moral teaching and communal ethos grow from the interweaving of scripture, canon law and local custom. The Church of the East regulated aspects of marriage, clerical discipline, fasting cycles and ecclesiastical administration through synodal canons; collections such as the Synodicon Orientale preserve many of these decisions and provide historians with concrete evidence about historical norms. Fasting cycles, including Lenten seasons and other fasts tied to the liturgical calendar, have been structured in relation to the Syriac lectionary and to pastoral demands tied to agricultural and communal rhythms. Sermons and catechetical instruction historically addressed issues of household life, charity, relations with neighboring communities and the duties of Christians living under non-Christian polities—concerns that remain salient where communities live as religious minorities.
The anthropology of suffering and the role of martyrdom occupy a prominent place in collective memory. East Syriac communities have often existed as dispersed minorities across the highlands of Anatolia, the Zagros, and the Mesopotamian plains, and they have experienced episodes of repression, forced migration and mass violence. Narratives of witnesses and martyrs—preserved in liturgical commemorations, local chronicles and hagiographical cycles—shape interpretive frameworks for suffering, resilience and pilgrimage. In modern memory, catastrophic episodes of the early twentieth century, including the mass violence of 1915 often referred to in Assyrian discourse as the Sayfo (sword) or Assyrian genocide, are central to communal remembrance and to contemporary diasporic identity; these memories inform liturgical commemorations, regional histories and patterns of migration.
There is notable internal diversity in emphasis and practice. Some dioceses and communities—particularly those historically centered on monastic networks in the plains and mountains around Nineveh, Hakkari and Urmia—tilt toward strong monastic and ascetic spirituality, while urban and diaspora communities increasingly emphasize pastoral care, education and institutional life, including schools and social services. Liturgical practice varies as well: classical Syriac remains the language of the liturgy, but local Neo-Aramaic dialects (commonly called Assyrian Neo-Aramaic or Sureth), Arabic, English and other vernaculars are used in preaching and in parts of the service in many parishes. Hymnography, chant traditions and the repertory of anaphorae show regional variation, and musical settings have adapted to local tonalities and congregational needs.
Comparative tensions have shaped the church’s relations with other Christian families. The East Syriac stress on dyophysite‑worded categories stands in tension with the miaphysite Christologies of the Oriental Orthodox churches (for example, the Syriac Orthodox Church) and with certain rhetorical formulations from the Byzantine Chalcedonian tradition; yet ecumenical dialogues in the late twentieth and early twenty‑first centuries—bilateral conversations with the Roman Catholic Church and with other Orient Christian communions—have produced statements of convergence that articulate common affirmations about Christ’s full divinity and humanity despite persistent terminological differences. Liturgically, the church’s Syriac language and many shared hymnographic themes place it in continuity with other Syriac-speaking traditions, even as its specific anaphorae, calendar practices and local customs mark distinctiveness.
In description and self-presentation, adherents maintain that their theology is faithful to the apostolic proclamation transmitted in Syriac-speaking Christian communities. Historians and theologians who study the tradition commonly map the church’s doctrinal development onto the political and linguistic realities of late antiquity—the Sasanian Empire’s religious landscape, the shifting borders of Roman and Persian jurisdictions, and the mobility of learned clergy—and on the institutional formations such as the ancient patriarchate seated historically at Seleucia-Ctesiphon. The result is a living worldview that combines a rigorous Christological vocabulary in Syriac, a sacramental and ascetic spirituality centered in monastery and parish, a robust scriptural tradition anchored in the Peshitta, and practices shaped by centuries of minority existence and wide geographical reach from Mesopotamia to the modern diaspora.