In April 1518, a pivotal event in Martin Luther's career took place in Heidelberg. This was the Heidelberg Disputation, where Luther defended his theology for the first time since the famous Ninety-Five Theses. In these theses, Luther not only defined the content of his theology of the cross but also presented his views on the differences between the love of God and the love of man.In his study, Kari Kopperi offers the first comprehensive analysis of this key Reformation text. The author scrutinizes Luther's theology of love, the theology of the cross, and Luther's understanding of the relationship between theology and philosophy. The theses of the Heidelberg Disputation are placed in a rich sixteenth-century context, and a new interpretation of their content is presented. Kopperi shows that several interpretations of the central theses of Luther's Reformation theology need to be revised, based on questions created by nineteenth-century neo-Protestant theology.