It is often asserted that Christian Trinitarianism was enforced by the political power of the emperor, e.g., Constantine the Great. However, Christianity largely succeeded in dominating Europe after the dissolution of the Western Roman Empire, so the successive reigns of individual emperors do not explain why the Church has upheld Trinitarianism. For nearly a millennium medieval Christendom and its Trinitarian ideology were rooted in feudalism. Under feudalism secular or temporal power was largely decentralised, so centrifugal rather than centripetal forces tended to dominate. There was no centralised state or bureaucracy to enforce doctrine, and in fact the Church, not the state or monarch, was the largest and wealthiest landowner. Furthermore, under these conditions doctrine would have been exposed to other influences, e.g., Judaeo-Islamic, monotheistic hermeneutical (“legalistic”) interpretation, via trade and war, given the absence of a unified, centralised secular authority over most of Europe. Even following the consolidation of the secular state during the Renaissance/Reformation, “reformed” modern Christendom upheld the Trinitarianism of its medieval Catholic forebear(s). Also, the Church Fathers/Doctors and early Protestant Reformers featured plenty of logical, intellectual giants, so why would they continue to uphold a transparently “illogical” doctrine such as that of the Trinity, given their otherwise logical approach to practical life, scholarship, and theology? For most of early Christian history political ambition cannot really explain why the Church as a whole adopted and did not abandon Trinitarianism, even in the absence of a single, centralised secular authority that could enforce such an “irrational” theological concept on its subjects. Medieval Europe was very decentralised, and the Church was more powerful than the emperor/monarch, so why would Trinitarianism be so uniform and persist, despite opposition by and exposure to Judaeo-Islamic monotheism via the Crusades etc.? One cannot blame the “secular” power for this.