Trinitarians have long criticized—and sometimes persecuted—non-Trinitarians for rejecting the doctrine of the Trinity. Early Arians, who denied the full divinity of Christ, were condemned as heretics by the First Council of Nicaea in 325 CE, and later non-Trinitarian movements, such as Unitarians, faced similar censure. Yet Trinitarians themselves have often rejected other Trinitarian interpretations. Many Oriental Orthodox churches—including the Coptic, Syriac, and Armenian churches—rejected the Council of Chalcedon in 451 CE, which defined Christ as fully divine and fully human “without confusion, without change, without division, without separation,” and were branded heretical by Chalcedonian Christians despite affirming the divinity of Christ. Likewise, the Eastern Orthodox and Roman Catholic Churches split over the Filioque clause—whether the Holy Spirit proceeds from the Father alone or from the Father and the Son—culminating in the Great Schism of 1054 CE. These examples show that those who claim to uphold “true Trinitarian doctrine” have often rejected other Trinitarian positions, revealing the complex and contested nature of Trinitarian theology throughout Christian history. The contrived nature of these disputes becomes particularly evident within each group: virtually no one challenges the group’s own adopted version of Trinitarian dogma. While Trinitarians condemn non-Trinitarians—or even other Trinitarians with slightly different formulations—for heresy, internal enforcement is rigid, highlighting that much of the controversy revolves less around theological truth than around maintaining institutional boundaries over what counts as “orthodox” belief.
