The Summa Theologica of the Archbishop Antonino Pierozzi, was a product of his preaching, and its themes were elaborations of topics that he expounded to his Florentine listeners. This new study demonstrates the integration of this Dominican friar’s theology with his preaching role and his audience’ concerns. It analyses the structure of the Summa, its complex functions and purposes. As the title promises, the study becomes a window into the intellectual, religious, social and political world of Renaissance Florence.