Recent studies of medieval preaching have tended to focus on sermon texts; this is the first full-length scholarly study in English of preaching and its social context in thirteenth-century Italy. Augustine Thompson O.P. reconstructs the 'Great Devotion' of 1233, and analyses its devotional, social, political, and legal elements. He shows how the preachers of this revival crafted an image of divine authority that supported their intervention in factional disputes and facilitated their arbitration in social and political conflicts. They exploited forms from revived Roman Law and developing city statutes to create flexible procedures for mediation, and ultimately were able to revise communal ordinances to enshrine their message of social harmony. This is a work of original scholarship, carefully researched and lucidly written, which is a valuable contribution to our understanding of religion and politics in the middle ages.