Luther justified his opposition to the rebels on three grounds. First, in choosing violence over lawful submission to the secular government, they were ignoring Christ's counsel to "Render unto Caesar the things that are Caesar's"; St. Paul had written in his epistle to the Romans 13:1–7 that all authorities are appointed by God and therefore should not be resisted. This reference from the Bible forms the foundation for the doctrine known as the Divine Right of Kings, or, in the German case, the divine right of the princes. Second, the violent actions of rebelling, robbing, and plundering placed the peasants "outside the law of God and Empire", so they deserved "death in body and soul, if only as highwaymen and murderers." Lastly, Luther charged the rebels with blasphemy for calling themselves "Christian brethren" and committing their sinful acts under the banner of the Gospel.