Paul's letter to the Galatians has been called "the Magna Charta of Christian Liberty". It has also been labeled "the short version of Romans", and "the cornerstone of the Protestant Reformation". In the early Church, as the great separation was taking place, the book of Galatians helped to clarify the doctrinal differences between "Judaism" and "Christianity". In fact, it constituted the main theme of the preaching of the Protestant Reformers in the first century and beyond.