Throughout the Middle Ages, the Catholic Church continued to assert its
             primacy of position. The growth of the papacy had paralleled the growth of the
             church, but by the end of the Middle Ages challenges to papal authority from
             the rising power of monarchical states had resulted in a loss of papal temporal
             authority. An even greater threat to papal authority and church unity arose in
             the sixteenth century when the unity of medieval European Christendom was
             irretrievably shattered by the Reformation.
             Martin Luther was the catalyst that precipitated the new movement. His
             personal struggle for religious certainty led him, against his will, to question the
             medieval system of salvation and the very authority of the church. His chief
             opposition was Holy Roman Emperor Charles V who, due to multiple
             circumstances, was unable to impede Luther's movement. He opposed the
             Catholic doctrine of faith and good works for salvation, instead proposing a
             doctrine of salvation through faith. His publishing of the Ninety-Five Theses,
             which covered the abuse of indulgences, is often seen as the beginning of the
             Reformation movement. However, the movement was not only confined to
             Luther's Germany.
             Native reform movements in Switzerland found leadership in Ulrich
             Zwingli, who eventually sought an alliance with Luther and the German
             reformers, and especially in John Calvin, whose Institutes of the Christian
             Religion became the most influential summary of the new theology. On most
             important doctrines, Calvin was in agreement with Luther. Calvin differed from
             Luther in his belief in the concept of predestination, derived from his belief in
             God's supreme authority. This concept became the central focus of succeeding
             generations of Calvinists.
             One of the more radical Reformation groups, the Anabaptists, set
             themselves against other Protestants as well as against Rome, rejecting such
             long-established practices as infant...