Expanding in part on earlier studies of the St. John Passion and the principle of “tonal allegory” in Bach's vocal music as a whole, this book investigates the musico‐theological character of the passion and the sequence of cantatas that followed its second performance in 1725. Citing many Lutheran authors from the 16th to the 18th century (with particular reference to August Hermann Francke and Johann Jacob Rambach), it attempts to show how Bach responded to the qualities that theologians have long recognized as characteristic of John, and that are now generally described as “Johannine.” Part One sets forth the research “problems” involved in the revisions to and versions of the passion as well as those surrounding the breaking off of the chorale cantata cycle just before Easter 1725 and the composition of the so‐called “Ziegler” cantatas. In addition it lays the conceptual groundwork for Part Two (a five‐chapter study of the St. John Passion) and Part Three (a study of the Spring 1725 cantatas). The book argues that in this unique series of compositions Bach reveals a thoroughgoing understanding of John's special qualities and devises special means of translating them into music.