The Leipzig Debate (German: Leipziger Disputation) was a theological disputation originally between Andreas Karlstadt, Martin Luther, Philipp Melanchthon, and Johann Eck. Eck, a defender of Catholic doctrine and a highly respected Dominican friar, had challenged Karlstadt, a Christian theologian, to a public debate concerning the doctrines of free will and grace. The Leipzig Debate took place in June and July 1519 at Pleissenburg Castle in Leipzig, Germany. Its purpose was to discuss Martin Luther's teachings, and was initiated and conducted in the presence of George, Duke of Saxony, an opponent of Luther. Eck, considered the master debater in Germany, was concerned about clerical abuses, but his life's work had been dedicated to the defence of Catholic teachings and combating heresy.
Eck invited Martin Luther to join the debate, and when Luther arrived in July he and Eck expanded the terms of the debate to include matters such as the existence of purgatory, the sale of indulgences, the need for and methods of penance, and the legitimacy of papal authority. Eck's debating skills led to Luther's open admissions of heresy in order to not be defeated. Luther declared that sola scriptura (scripture alone) was the basis of Christian belief, that the Pope had no power as he was not mentioned in the Bible, and condemned the sale of indulgences to the laity to reduce their time in purgatory, as there was no mention of purgatory in the Bible.