What really motivated Luther's heart was his shepherding concern. So often people misunderstand Luther. There are errors in Luther; he was not perfect by any stretch of the imagination. At times he could be caustic and harsh, but even in understanding that, one of the helpful things is to put oneself in Luther's place and realize what he was up against and the challengeshe faced and understand that what really burdened his heart was the welfare of the sheep that he cared about so much in Wittenberg. He wanted them to experience the liberation that he had experienced from the torment of guilt and of being trapped in the guilt of the Roman Catholic system which does not offer life but kills. So when Luther came to be delivered from that through the word of God and through studying the Bible and seeing that salvation comes by grace alone, through faith alone, in Christ alone, the liberation of that motivated his heart with a passion that others might know that freedom. So when he saw the Catholic Church resisting the preaching of the word of God, trying to stifle that and to keep people trapped in the same darkness, he was rightly angered and motivated to preach the word. So as we understand his heart, he wanted to shepherd those souls of those people in Germany who were entrusted to him and he wrote so that people throughout Europe could be delivered from that darkness.