God and Prince in Bach's Cantatas

All the modern critics of J. S. Bach have been worried by his habit of introducing into a choral work a number which he had already used in an earlier cantata.' They have excused the practice on the grounds that such self-plagiarism was common at the time, that Bach was always working at top pressure, and that, since his works were not printed, any one cantata might only be heard by a small audience, so that he could safely introduce a piece from it into another work intended for a different group of listeners. But they are more baffled, and even distressed, when they find the same number appearing in both a secular and a religious work.2 How, they say, can Bach, who was such a scrupulously honest musician, and who paid such attention to the appropriateness of his music to the words he was setting, use the same aria to celebrate a German princeling and to accompany a meditation on the life of Christ ?