Preface: This article was written in collaboration with ChatGPT.

Before Protestantism formally emerged, Europe had already seen important “pre-Reformation” movements, the most significant of which was the Hussites. The Hussite movement arose in early fifteenth-century Bohemia, with its intellectual core shaped by the theologian Jan Hus. Hus argued that Scripture stood above church authority, opposed ecclesiastical corruption, called for preaching in the vernacular, and criticized indulgences and clerical privilege. He did not seek to found a new denomination; rather, he directly challenged the power structure of the Roman Church. After Hus was burned at the stake in 1415, Bohemia was plunged into the prolonged Hussite Wars, transforming what had begun as a theological dispute into a political conflict deeply intertwined with religion and national identity. Although the Hussites did not develop a fully systematized Protestant theology, they demonstrated—both chronologically and intellectually—that the authority of the Roman Church was not beyond challenge. For this reason, they are often regarded as “Protestantism before Protestantism.”

The earliest fully formed Protestant tradition was Lutheranism, which emerged directly from Martin Luther’s reform in the German lands. The theological core of Lutheranism is justification by faith alone: salvation depends entirely on faith, not on good works or church institutions. Lutheranism categorically rejected papal supremacy, yet remained relatively conservative in church structure and liturgical practice, preserving many outward forms inherited from the medieval church. Politically, Lutheranism showed a high degree of accommodation to secular authority, holding that the state bore responsibility for maintaining church order. As a result, it often became a state-supported church in Germany and Northern Europe. This orientation contributed to relative social stability and limited the tendency toward moral or political radicalism.

Compared with Lutheranism, the Reformed tradition (Calvinism) was more thoroughgoing both theologically and disciplinarily. It developed in Switzerland and the French-speaking regions, and its intellectual system was consolidated by John Calvin. Reformed theology emphasized God’s absolute sovereignty and predestination, asserting that salvation does not rest on human choice but on divine will. Consequently, the Reformed churches placed extraordinary weight on church discipline and moral order, rejecting all rituals and adornments that lacked explicit biblical warrant. In Geneva, Calvin promoted a highly regulated religious community in which the church governed not only belief but also daily life. The Puritans, the Scottish Presbyterian Church, the Dutch Reformed tradition, and the New England tradition in North America all largely inherited this lineage.

The English Reformation followed a markedly different path, culminating in the formation of Anglicanism, or the Church of England. This system was not driven by theologians but established directly under state leadership. Theologically, it affirmed the authority of Scripture and rejected papal supremacy, placing it within the Protestant camp. Institutionally and liturgically, however, it retained many elements of Catholic tradition, including the episcopal system, sacramental structures, and clerical vestments. This compromise produced considerable political stability, yet generated persistent religious dissatisfaction. It was precisely within this tension that the Puritans emerged from inside the Church of England, repeatedly criticizing the reform for its lack of thoroughness.

The most radical—and least tolerated—current of the Reformation was the Anabaptists. They rejected infant baptism and insisted that only adults who consciously professed faith could be baptized, rendering all infant baptisms invalid and requiring rebaptism. This position not only challenged church tradition but also struck at the institutional foundation through which states used the church to manage population and social order. Many Anabaptist groups refused oaths, military service, and in some cases denied the sacred legitimacy of secular government altogether. As a result, they were treated as dangerous subversives and brutally persecuted by both Catholic and Protestant authorities. Yet their ideas of voluntary faith, religious freedom, and the separation of church and state later became widely accepted principles of modern society.

If the Anabaptists challenged the alliance between church and state, Unitarianism went further by questioning the core doctrines of Christianity itself. Emerging in the mid-to-late sixteenth century, Unitarians were active primarily in Poland, Hungary (Transylvania), and among Italian intellectuals in exile. Their most controversial position was the rejection of the Trinity in favor of strict monotheism, holding that Jesus was a divinely chosen moral exemplar rather than a being of the same substance as God. This stance led both Catholics and mainstream Protestants to condemn them as heretical. One of their prominent figures, Michael Servetus, was executed for denying the Trinity, starkly revealing how narrow the boundaries of theological tolerance remained even within the Protestant camp.

The Puritans were not an independent Protestant denomination but an ongoing reform movement within the English Protestant context. Deeply influenced by Reformed theology, they operated primarily inside the Church of England. The Puritans believed that although England had broken with Rome, its church and society were still riddled with “impurities” inherited from Catholicism. They opposed episcopal governance, elaborate rituals, and hierarchical clergy, and emphasized strict moral conduct and communal discipline. Because these ideals proved difficult to realize in England, some Puritans ultimately chose to leave, migrating to North America and undertaking new social experiments in New England.

Viewed together, these movements clarify the internal dynamics of Protestant formation. The Hussites challenged the legitimacy of church authority and served as a precursor to Protestantism; Lutheranism and the Reformed tradition addressed questions of salvation and interpretive authority; Anglicanism mediated the conflict between state sovereignty and religious order; the Anabaptists questioned the very premise of church–state co-governance; and Unitarianism tested the outer limits of what Christian theology could tolerate. The varied breakthroughs, failures, and fragmentations along these different trajectories together produced a Protestant tradition that was anything but uniform, yet rich in historical tension and consequence.