“When the sale of indulgences by Johann Tetzel was undertaken in Saxony [Martin Luther’s] sense of duty was stirred to the quick, and on that memorable October 31, 1517, he nailed his Ninety-five Theses as a declaration and a challenge. The Theses were ninety-five, but the theme is one. Men cannot be made just before God by works of any kind, but by faith alone. This was called the material principle of the Reformation.” — Andrew C. Zenos, “The Reformers as Men of Thought and Action” in The Protestant Reformation and Its Influence, 1517-1917: Addresses Delivered in Connection with the One Hundred and Twenty-Ninth General Assembly of the Presbyterian Church in the United States of America at Dallas, Texas, on May 19 and 20, 1917 (1917)