In his more than 200 cantatas Bach interprets the human condition through musical assertion and examination of the relevance of the gospels and epistles of the Christian Bible. Every cantata is discussed in my six book series . The epistle, which is essentially didactic, is from the Apostolic letters retained in Scripture. The gospel, which is concerned with the life and teachings of Christ, is effectively an exposition of His adherence to principles and the application of action. Guided by this context, Bach consistently propounds surpassing interpretations of the nature and spirit of life. Though the over-reaching principles are philosophical and ethical, how they apply is determined, ultimately, by the individual. Book Four of this series examines the 31 surviving cantatas for the Sundays and feast days from Advent throuhg Christmas and New Year to Epiphany, and includes the six cantatas of the Christmas Oratorio, and one secular cantata. There are individual chapters on Advent, Christmas, the Feast of St. Stephen, the Feast of John the Evangelist, the Christian Bible, and the life of Christ, as primarily found in the canonical gospels of Matthew, Mark, Luke, and John. Bach, in these, affirms and explains such fundamental aspects as divine protection and favour, illumination of the soul, fate, and the trials of existence. It is a personal exploration, both his and mine.