Definition
Erastianism is the doctrine that the state has supremacy over the church in ecclesiastical matters. It asserts that the state, not the church, should have the final say in matters of religious law and administration. Think of it as the principal of a school having more power than the head of the religious studies department. Itβs about secular authority having control over religious affairs. Erastianism has historically been controversial, with many arguing for the separation of church and state.