Lutheranism is a movement within Christianity that began with the theological insights of Martin Luther in the 16th century. Luther's writings launched the Protestant Reformation. This attempt to reform the theology and practice of the Catholic Church led to the separation between a large number of Christians and the Roman Catholic tradition.MSN Encarta, s.v. "http://encarta.msn.com/encyclopedia_761561935/Lutheranism.html Lutheranism" by George Wolfgang Forell; Christian Cyclopedia, s.v. "http://www.lcms.org/ca/www/cyclopedia/02/display.asp?t1=r&word=REFORMATION.LUTHERAN Reformation, Lutheran" by Theore Hoyer.