On October 31, 1517, Martin Luther, an Augustinian monk posted a document on the door of a church in Germany that sparked the Reformation. Luther emphasized three major concepts that challenged the prevailing religious and political system.

Grace Alone – the conviction that salvation is the free gift of God's grace and is undeserved. This "inborn sickness and hereditary sin" makes it impossible to earn forgiveness. This is the concept that "Jesus Christ, true God, begotten of the Father from eternity, and also true man, born of the virgin Mary, is my Lord, who has redeemed me, a lost and condemned person … not with gold or silver, but with his holy, precious blood and with his innocent suffering and death…." (Luther's Small Catechism with Explanations, p. 14)

Faith Alone – the grace of God "can be appropriated by sinful human beings only through faith." This broke from the works-based doctrine that had prevailed in the Catholic Church throughout the Middle Ages. Luther believed that because of this, Christians were at the same time sinners and saints. Through faith in Christ, sinners would be forgiven and right with God.

Scripture Alone – the Bible is the Word of God and does not need to be interpreted through anybody else, including the church which are not infallible. But confidence in Scripture is not possible apart from faith in Jesus Christ.

Luther's assertions caused people to question the power of the medieval church and its corresponding political power, and his belief in the priesthood of all believers led to notions of equality of all before God.

For more information on what Lutherans believe check out Dr. Samuel Nafzger's article, "What Do Lutherans Believe."

In celebration of the 500th Anniversary of the beginning of the Reformation, we asked some thought leaders to discuss Luther's impact on society and religion.