On October 31, 1517, he posted a challenge on the church door at Wittenberg University to debate 95 theological issues. Luther's hope was that the church would reform its practice to be more consistent with the Bible. What started as an academic debate escalated to a religious war; as a result, there was not a reformation of the church but a separation. “Lutheran” was a name applied to Luther and his followers as an insult but they adopted it as a badge of honor instead.

Lutherans still hold to the basic principles of theology and practice espoused by Luther, such as:

• We are saved by the grace of God along—not by what we do;
• Our salvation is through faith alone—we only need to believe that our sins are forgiven for Christ's sake, who died to redeem us;
• The Bible is the only norm of doctrine and life—the only true statement by which teachings and doctrines are to be judged.

Luther's Small Catechism (which contains basic teachings on the Ten Commandments, the Apostles' Creed, the Lord's Prayer, Holy Baptism, and Holy Communion) is still used to introduce people to the Lutheran faith, as is the more detailed Augsburg Confession. These and other Lutheran confessional documents are included in the Book of Concord.

Martin Luther’s Seal

Martin Luther created his seal while he was a professor at Wittenberg University. The seal was meant to be “expressive of his theology.” The seal shows a cross on a heart at the center of a rose. The Messianic rose symbolizes Christ and is enclosed in a circle that denotes eternity. This explanation is taken from a letter written to his friend, Herr Spengler, the town clerk of Nuremberg.

The first thing expressed in my seal is a cross, black, within the heart, to put me in mind that faith in Christ crucified saves us. “For with the heart man believeth unto righteousness.”

Now, although the cross is black, mortified, and intended to cause pain, yet it does not change the colour of the heart, does not destroy nature—i.e., does not kill, but keeps alive. “For the just shall live by faith.”—by faith in the Saviour.