The Reformation and post-Reformation eras were marked by major episodes of theological controversy. Registering high on the Richter scale were debates regarding predestination and the doctrines of grace, which troubled every major Christian tradition. The Eastern Orthodox Church faced the apparent conversion of a former Patriarch of Constantinople to Calvinism as witnessed in The Confession of Cyril Lukaris (1631). The controversy culminated in the Synod of Jerusalem (1672), whose Confession of Dositheos condemned Calvinist doctrines as ‘abominable, impious, and blasphemous’. In 1581, debate flared within the Roman Catholic communion as a Dominican friar, Domingo Báñez, accused Jesuit priests of reducing grace to synergistic aid (auxilia) rather than efficacious infusion. The publication in 1588 of Concordia Liberi Arbitrii by the Spanish Jesuit Luis de Molina added fuel to the fire. By 1602 Pope Clement VIII presided over a series of formal conferences in a bid to resolve what became known as the controversy de Auxiliis. After eighty-five conferences, the verdict was inconclusive and a papal decree in 1607 permitted both Dominican and Jesuit doctrines of grace. A later decree in 1611 forbade further publications regarding efficacious grace in a bid to dampen the flames of controversy that still raged. However, the writings of Cornelius Jansen reignited the controversy in 1640 when his three-volume work was posthumously published, in which Jesuits were denounced as Pelagiani moderni. Finally, in 1653 Pope Innocent X condemned the five cardinal doctrines of Jansenism as heresy, though the dispute continued to simmer under the surface into the eighteenth century.

Within Lutheranism, a synergistic controversy also erupted and deepened divisions between the self-styled ‘Gnesio’ or ‘genuine’ Lutherans and the Philippists who followed Melancthon. Johann Pfeffinger and other Melancthonians contended for human cooperation in conversion, insisting that sufficient modus agendi (mode of action) was available to fallen humanity to respond to divine grace, contra Luther's De Servo Arbitrio.