The third significant schism was the breaking away of the evangelical and reformed churches under Luther and Calvin in the sixteenth century. There is a case for saying the Reformation brought long-overdue corrections and renewal, both in the churches that originated from it and, by reacting to it (as in the Council of Trent, 1545–1563, the major event in what is called the Counter-Reformation), in the Roman Catholic communion. A more complete account of the roots of the Reformation is found in Chapter 13.

The leaders of the Reformation — Luther, Calvin, Zwingli, Cranmer, and others — set out to reform the one Catholic Church they knew, not to create new churches, or what came to be called denominations. But they set in motion a process that led to that end, and continues to produce new denominations to fit every taste in doctrine, liturgy, polity, and ecclesiology.